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“Better head for shore, Frank! It’s blowing up a gale!”

Frank Hardy, at the steering wheel of the Sleuth, glanced up at the sky. Heavy black clouds were gathering and a gusty wind was whipping the waters of Barmet Bay into foam. The trim little motorboat was beginning to pitch and roll in the swell.

“I guess you’re right, Joe,” he said to his brother. “I’ll swing her around.”

Frank bore down on the wheel and brought the bow of the craft about so that it was once more heading toward the city of Bayport. One of the conditions on which the boys had been allowed to own the Sleuth was that they must not run unnecessary risks. The bay always was treacherous and subject to sudden squalls.

The motorboat was just speeding back down the bay when the storm broke. There was a howling gust of wind, a few slashing streaks of rain, a flash of lightning, a roll of thunder. Then the skies seemed to open. The rain fell in a torrential downpour. Bayport was completely obscured from view.

Frank Hardy, a dark, good-looking boy of seventeen, crouched at the wheel and peered out across the tossing waste of waters. Joe threw him an oilskin coat and sou’wester and struggled into a similar outfit himself.

The little motorboat was cutting easily through the waves, the engine pounding away without a miss.

“It won’t last long!” Frank shouted.

The storm seemed to sweep the tumultuous surface of the bay like a great gray broom from the skies. The wind moaned and whistled overhead.

In a few minutes the squall was passing, roaring on out toward the sea. The rain diminished. The buildings of Bayport began to appear dimly ahead.

“Another boat nearby!” said Joe, gazing out over the water. He could hear the rapid throb of an engine. The sound came from over to their right. A moment later he caught sight of a dark shape streaking through the storm.

The other craft, which was big and powerful, was traveling at high speed, its bow rising high out of the water. And it was rushing straight toward the Sleuth!

Joe expected to see the boat alter its course. But it drew swiftly nearer, bearing down on their own craft. Suddenly he realized that a collision would be only a matter of seconds.

“Hey! Look out!” he yelled.

The other boat came roaring swiftly toward them. Frank Hardy juggled the wheel, and swung the Sleuth around in a dangerous turn. A huge wave crashed against the side. The boys were drenched with water. Joe uttered a cry of alarm when he saw the big powerboat looming right at their stern, within an ace of running them down.

Frank swung the wheel over again in a desperate effort to avoid a crash. He was just in the nick of time. The stern, sheered away when it seemed that the prow of the other boat was about to go through it. Nevertheless, there was a sudden jarring shock as their craft was clipped by the other.

The boys caught a glimpse of the man at the wheel. He was a swarthy fellow, black-haired, handsome in a way, but unpleasant looking. A moment later the big powerboat was racing away from them in a boiling flurry of foam.

“He didn’t even slow up to see what damage was done!” cried Frank angrily. “We might have drowned out here for all he cared.”

Joe looked over the side.

“There’s a big dent here and the paint is all scratched, but I don’t think the boat is leaking,” he announced. “Mighty lucky you pulled around when you did.”

“Why, that fellow is as bad as a hit-and-run motorist on land. I’m going after him. Did you recognize him, Joe?”

“Never saw him before. He looked like a foreigner to me.”

Frank Hardy swung the bow of the motorboat in the direction of Bayport and opened the throttle wide as he took after the other craft. But the Sleuth, reliable as it was, proved to be no match for the fugitive. Within a few minutes the powerboat was only a tiny speck on the tossing waters and the Hardy boys were left far behind in its wake.

“I can’t figure it out,” said Joe, mystified. “There are faster boats than ours on Barmet Bay, but I’ve never seen one that fast.”

“He must be a stranger. Probably from one of the towns up the coast.”

By the time the Hardy boys reached the calmer water of the harbor there was no sign of the man they were chasing.

“I’d like to meet that fellow and tell him what I think of him,” Frank said, steering the Sleuth into their own boat-house. They knew that there had been no excuse for the accident and that it might easily have been more serious, perhaps fatal to both of them.

While they were examining the damage, the door opened.

“What ho! What ho, my cheery mariners!” exclaimed a familiar voice. “Welcome ashore, mates, after your voyage on the vasty deep.”

A short, stout boy with a good-natured face came in, munching an apple. He was Chet Morton, a close chum of the Hardy boys. Chet was a fun-loving lad, and the butt of many jokes because of his desires for food. He was always hungry and he admitted it.

“I was looking for you fellows,” he announced. “Let’s go up to the Federal Court. My father is on the jury and there’s an exciting case going on.”

“What’s it about?” they asked, interested.

“The Rio Oil Company fraud. You know—the crowd that sold so much Mexican oil stock around Bayport. If you want to hear the case you’d better hurry.”

The Hardy boys agreed to go, and hastily tied their boat in the slip. Chet noted the damaged side, and wanted to know the details. The Hardys told him about the swarthy man who had come so close to wrecking them in the bay.

“Why, that must be Sandy MacPherson’s big new powerboat!” exclaimed Chet. “I was watching the engine being tested the other day. It just arrived from the factory the first part of the week.”

Sandy MacPherson was an elderly Scot who managed a boat livery not far down the shore. The Hardy boys knew it had long been his ambition to own a speedy craft that could show its heels to any other boat on Barmet Bay.

“Let’s drop in and ask him before we go up to the court,” Frank suggested.

The boys found Sandy MacPherson fondly admiring a big, powerful boat that they recognized at once.

“That’s it, all right!” shouted Joe. “Who was out in your boat, Sandy?”

“I dinna ken the mon’s name,” replied Sandy. “He hired the boat frae me just t’other day. A furrin lad he was. He hired the boat and he brocht it back and he paid me weel.”

“A foreigner?”

“Aye! He couldna speak English verra weel. Could scarcely unnerstan’ me.”

“And you don’t know anything more about the man?”

Sandy shook his head.

“The mon minded his ain business. And I mind mine,” he observed significantly.

Disappointed, the Hardy boys and Chet left the boat livery and went up the street.

“Forget it,” advised Chet. “Let’s hurry, or the case will be over before we hear any of it.”

When the boys made their way into the Federal Court ten minutes later they found the place crowded. All Bayport was interested in the sensational Rio Oil case. Scores of citizens had invested their money in shares of the stock that had been peddled by smooth and convincing salesmen. The arrest of the promoters, and the discovery that the wells—which were said to be in Mexico—had never produced a drop of oil and never would, were developments that had been emblazoned in newspaper headlines for days.

The boys slipped into seats just in time to hear the District Attorney questioning one of the Rio Company’s stock salesmen. He was a suave, shifty-eyed fellow who did not seem to be the least bit at ease in the witness box.

“You sold three thousand shares of this stock to Mrs. Margaret Chadwick?” asked the District Attorney sharply.

“Yes, sir.”

“She is a widow?”

“So I believe.”

“It was all the money she had?”

“I—I think so.”

“And you knew the stock was worthless?”

“I didn’t know anything about it. I was just obeying orders.”

“And your orders were——?”

“To sell as much stock as I could.”

At this moment an attendant pushed his way through the crowd and handed the District Attorney a note.

“If the court will excuse me,” the latter said to the Judge, “I should like to read this communication.”

Frowning, he glanced at the note. Then he appeared much upset.

“Your Honor,” he said abruptly, “I am sorry, but I must ask for a postponement of this case.”

“Upon what grounds?” asked the Judge.

“I have just received word that my principal witness, Mr. Tremmer, has mysteriously disappeared. Inasmuch as he was the bookkeeper of the Rio Oil Company, he is in possession of a great deal of evidence highly important to my case. It is impossible for me to proceed without him.”

The Judge considered briefly.

“Very well,” he said. “I shall grant you a stay of twenty-four hours. Court stands adjourned.”

The District Attorney’s announcement that his star witness had disappeared created a sensation in the courtroom. A buzz of voices arose when the Judge left the bench.

“Dirty work in this case,” said Chet. “I’ll bet the Rio crowd had something to do with that disappearance. The State can’t very well get a conviction without Tremmer’s evidence.”

But Frank was not listening. Suddenly he grabbed his brother’s arm.

“Look, Joe!” he exclaimed. “Isn’t that man over there the one who damaged our boat a while ago?”

He was gazing in the direction of a crowd of men near the doorway. Among them was a tall, swarthy, black-haired stranger who seemed to be in a hurry to get out of the courtroom. Joe took one look and exclaimed:

“That’s the fellow! Come on, Frank! Let’s get him before we lose him in the crowd outside.”

The Hardy boys scrambled into the aisle, closely followed by Chet. They were held back by the dense crowd, however, and by the time they reached the doorway they had lost sight of their quarry. Vainly they searched the corridor outside the courtroom.

“I’ll bet he saw us first!” said Joe bitterly.

“We’re going to find that fellow!” Frank declared. “We’re going to find him and make him pay for the damage to our boat.”

“I’m sure he saw us and got out of the courtroom as quickly as he could because he was afraid to face us,” insisted Frank Hardy.

“Brave words, my hearty!” Chet said. “But how are you going to find him? Why not put an ad in the newspaper? ‘Will the foreign gentleman who busted our boat on Thursday afternoon please call at our house and pay for same.’ Maybe that will fetch him soon enough.”

The boys asked some of the courtroom attendants and the doorman if they remembered the swarthy stranger, but their inquiries met with no success. When Frank and Joe Hardy tackled a problem they did not give up easily and insisted that they would locate the man sooner or later. Chet was highly amused.

“There are several thousand people in Bayport,” he laughed, “and you know the fellow only by sight. You’ve never heard his name or where he lives or anything.”

“Just the same, we’ll find him!”

The trio went on down the chief business street of Bayport, discussing the mysterious stranger and the odd turn of events that had caused the postponement of the Rio Oil trial.

“My father said that this bookkeeper, Tremmer, was going to give evidence for the State, and that the District Attorney was relying on him to prove that the oil promoters were a pack of crooks,” said Chet. “It seems funny that he should disappear just at this time.”

“It’s more than funny. It’s suspicious,” Joe remarked. “Perhaps they gave him some money and he left the country.”

“Tremmer wouldn’t do that. He’s honest. That is why so many people put faith in the company. They thought that if Tremmer was connected with it, the stock must be all right.”

“Lots of people lost all their savings,” said Frank. “Do you think they’ll get their money back if the State wins the case?”

“The promoters didn’t have time to get away with the money. It seems that Tremmer got suspicious and tipped off the Secret Service.”

Down the pavement marched an angular woman with a determined stride. She had a grim, severe face. A pair of spectacles perched precariously on the end of her nose.

“Aunt Gertrude!” exclaimed Frank.

“Let’s get out of sight!” exclaimed Chet, who had a wholesome dread of the formidable old lady.

They were too late, however. Aunt Gertrude had an eye like a hawk and had seen them already. She bore down as relentlessly as the swarthy stranger’s powerboat. Aunt Gertrude was a spinster of uncertain age who “visited” one relative after another. Just now she was installed at the Hardy home on one of her periodical visits. She was a gruff, outspoken woman, but the Hardy boys knew that her bark was worse than her bite.

“Ha!” she exclaimed. “So here you are! Loafing about the streets, eh?”

“We aren’t loafing, Aunt,” said Frank. “We were just over at the court house listening to a trial.”

“Stay away from court houses!” ordered Aunt Gertrude. “Court houses mean crime. If there was no crime there would be no court houses. And crime means jail. And jail means disgrace. Stay away from ’em. I nearly got bitten by a dog.”

Aunt Gertrude had a way of jumping from one subject to another in a manner that was disconcerting to those who did not know her.

“Nearly got bitten, Aunt Gertrude!” exclaimed Joe.

“Lucky for the dog that it was only nearly,” murmured Chet.

“What’s that, young man?” demanded Aunt Gertrude, glaring at him over the top of her spectacles. “What was that remark?”

“I said I’m glad it was only nearly,” said Chet meekly. “I’m glad he didn’t really bite you, ma’am.”

“Dogs shouldn’t be allowed!” said Aunt Gertrude. “Nasty little brutes. I’ll report that woman.”

“What woman?” asked Frank.

“Why, the woman who owned the dog. Don’t be so stupid!” cried his aunt. “What other woman should I be talking about? I’ll report her. And such a dog. If people must own dogs let them own dogs, not an apology for a dog. Not an imitation dog. My goodness, this dog was actually naked!”

“A naked dog!” exclaimed Joe.

“Not a hair on its hide! If I had a dog like that I should put hair tonic on it. Said a Mexican gave it to her. Bah!”

Frank was interested.

“A Mexican! Then it was a Mexican hairless dog, probably.”

Aunt Gertrude cupped her hand to her ear.

“Eh? A Mexican heiress?”

“A Mexican hairless. Who owns it, Aunt Gertrude?”

“Mrs. Smith, the woman who runs the boarding house two blocks from home. She said one of her boarders gave it to her. And it tried to bite me. If I ever meet that boarder I’ll give him a piece of my mind. Going around handing out naked dogs that try to bite people when they’re walking quietly along minding their own business! Outrageous. Go home!”

With that, Aunt Gertrude marched on her way. Chet whistled softly and mopped his brow with relief.

“That must have been either a doggone brave dog or a doggone foolish dog, to try to take a bite out of her!” he remarked.

Frank was thoughtful.

“So there’s a Mexican boarder at Mrs. Smith’s place,” he said meaningly.

Joe looked up.

“That fellow did look something like a Mexican!” he exclaimed.

“Maybe it’s a clue. We’ll look into it.”

“Clue!” snorted Chet. “Probably some poor, innocent old fellow who doesn’t even know how to run a motorboat. However, I’ll tag along. I’d like to see that hairless dog anyway.”

While the Hardy boys and Chet are on their way to the boarding house to investigate Mrs. Smith’s lodger from Mexico, let me introduce the lads more fully to my readers.

Frank and Joe Hardy were the sons of Fenton Hardy, famous detective who had retired after a brilliant career with the New York Police Department, to launch out professionally for himself. So successful had he been that he was known throughout the United States as one of the shrewdest criminal investigators in the country.

Although Mr. Hardy had not planned that his sons should follow in his footsteps, it soon became apparent that they had inherited his deductive talents. In the opening volume of this series, “The Hardy Boys: The Tower Treasure,” the two brothers succeeded in solving a mystery that had baffled the Bayport police, and recovered a rich treasure from its hiding place. From then on Frank and Joe were determined to carve out careers for themselves as detectives. Many of the puzzling mysteries that they solved have been recounted in the various books in this series, such as “The Secret of the Old Mill,” “Hunting for Hidden Gold,” and others.

In “Footprints Under the Window,” the preceding volume, the boys investigated a weird mystery surrounding an apparently innocent Chinese laundry in Bayport, and succeeded in clearing up a case upon which Fenton Hardy himself had been engaged.

As the chums walked toward Mrs. Smith’s boarding house they had no idea that their efforts to locate the swarthy stranger were about to involve them in one of the most thrilling adventures of their lives.

Mrs. Smith, a sweet, kindly old lady whom they knew well, was surprised when she learned the object of their visit.

“Why, yes,” she said, when they asked about her lodger. “I have a Mexican boarding here. At least, I had. He left not ten minutes ago. His name was Pedro Vincenzo.”

“Has he gone for good?” asked Frank, keenly disappointed.

“I’m afraid so,” replied Mrs. Smith. “He was away for the past two days but returned a short time ago, packed up, and left. He paid me in a peculiar manner, too—not with cash, but by a lot of pieces of paper that he said would bring me plenty of money.”

The Hardy boys were just on the point of asking Mrs. Smith if she would let them see the papers, when there was a sudden disturbance from the upper part of the house. A maid screamed wildly, and ran down the stairs.

“The dog, ma’am!” she shrieked. “The dog! He’s gone mad.”

The boys could hear an animal barking and yelping. Mrs. Smith was badly frightened. Her face turned pale, and she clung to the banister for support.

Frank reached the stairs at a bound and hastened to the upper floor, Joe and Chet close at his heels. In the hall he found a Mexican hairless pup writhing and twisting on the floor.

“He’s not mad!” cried Chet. “He is having a fit. Throw some water on him.”

Frank located the bathroom, quickly filled a glass with water, ran back, and dashed the contents over the squirming animal. After a few trips the dog was thoroughly drenched, becoming quieter as he came out of the fit. Finally he crawled away, whining.

Mrs. Smith, who had watched these proceedings from the stairway, was greatly relieved.

“Then he isn’t mad after all?” she inquired anxiously.

“I think he’ll be all right now,” said Frank. “Maybe it wouldn’t be a bad idea to call a veterinary surgeon to have a look at him.”

Mrs. Smith picked up the quivering little animal and it lay in her arms, shivering.

“Mr. Vincenzo gave me this dog,” she explained. “I’ve become greatly attached to the little animal.” She indicated an open doorway nearby. “That was Mr. Vincenzo’s room.”

Frank and Joe stepped into the chamber. It was clean and neat. Vincenzo had taken away all his belongings. Nothing remained to indicate the character of the previous occupant so far as they could see.

“Even if he was the man we’re looking for,” said Joe quietly, “I guess we’ve lost track of him now.”

“I’m afraid so,” admitted Frank. “We may as well go.”

Joe’s sharp eyes suddenly caught sight of something that interested him.

“That’s queer!” he exclaimed, going over to the door. “I wonder if it’s Mr. Vincenzo’s work.”

Mystified, Frank followed him while Joe swung the door partly shut. There, in the woodwork, the boys saw a peculiar mark burned into the back of the door.

It was a strange symbol, very neatly executed, and represented a heap of blazing sticks with the initial P in the center of the flames.

That evening the Rio Oil Company case was the chief topic of conversation at the Hardy dinner table. The newspapers were filled with the story of Elmer Tremmer’s sudden disappearance just when his evidence was needed by the authorities.

“What do you think happened to him, Dad?” asked Frank of his father.

Fenton Hardy smiled.

“I haven’t the least idea,” he said, “but I hope to find out.”

“Are you working on the case?” cried Joe.

“Yes, the stockholders of the oil company have retained me to try to locate Tremmer.”

“Do you think he ran away?”

“Elmer Tremmer was never very long on brains,” said Mr. Hardy, “but I would bank on his honesty. That’s why the swindlers made him bookkeeper of the company—because they imagined he wouldn’t be smart enough to see through their crooked work and would at the same time convince everybody in Bayport that it was a legitimate enterprise. No, I don’t believe Tremmer ran away. After all, it was on his information that the authorities first took action against the company.”

“Perhaps he was kidnaped!” Frank suggested.

“That is a possibility,” Fenton Hardy agreed. “Then again, the crooks may have frightened him into going away. I have picked up a few clues that may lead to something.”

“Do you know if a man named Pedro Vincenzo had anything to do with the Rio Oil fraud?” asked Joe.

“Not to my knowledge. I have never heard the name mentioned.”

“Weren’t there some Mexicans at the head of the concern?”

“The oil wells were supposed to be in Mexico and two or three of the directors were from that country. The others were Americans.”

That evening, when the boys were discussing the affair, they agreed that Pedro Vincenzo might well have been involved in the oil company fraud even if his name had not come to light.

“Mexicans aren’t so numerous in this part of the United States,” Frank argued. “It seems queer that he checked out of his boarding house just as soon as he knew the trial was postponed. He was certainly interested in the trial or he wouldn’t have been in the courtroom.”

“I vote we go back to Mrs. Smith’s house tomorrow and ask her a few more questions about the fellow,” said Joe.

“We may as well do a little detective work on our own account. Perhaps we’ll learn something that will help Dad.”

Next morning, after going down to the boat-house to inspect the damage done to the Sleuth and turn the craft over to Sandy MacPherson for the necessary repairs, the Hardy boys again called on Mrs. Smith.

They found the little old lady mourning the loss of her dog. The animal had died during the night.

“Oh, dear!” said Mrs. Smith, “I was so attached to the poor fellow and now I don’t suppose I’ll ever be able to get another dog quite like him.”

“Perhaps the climate didn’t agree with him,” Joe suggested.

Mrs. Smith thought otherwise. She would never buy a dog to replace her pet unless she could get another Mexican hairless. Frank and Joe gradually led the conversation around to the subject of Pedro Vincenzo, the boarder who had given her the animal.

“What sort of a man was he?” asked Frank.

“He was very polite,” said Mrs. Smith, “but he was also very conceited. To hear him talk you would think he had been one of the greatest men in Mexico. He bragged a little too much to suit me. He used to tell me the most terrible stories about Mexican bandits—dreadful people. And he actually joked about some of the things those bandits did. He said he came from a place where people lived in the cliffs.”

“By the way,” Joe remarked, “you told us yesterday that he didn’t pay you in money but in pieces of paper. What were they?”

“I don’t rightly know,” said Mrs. Smith. “He said they would be very valuable some day. They have something to do with oil. I’ll go and get them.”

Joe glanced significantly at his brother, when Mrs. Smith went into the next room and rummaged through an old desk.

“Oil certificates, I’ll bet a hat,” he murmured.

Joe was right. Mrs. Smith returned with half a dozen gaudily printed documents that proved to be certificates for five thousand shares of Rio Oil Company stock.

“Are they worth much?” she asked anxiously.

“Haven’t you been reading the newspapers?” asked Frank.

“My eyes have been bad lately. I haven’t looked at a paper in weeks.”

“Mr. Vincenzo must have known that. I’m afraid you have been swindled, Mrs. Smith.”

The Hardy boys then told her about the Rio Oil fraud and the interrupted trial. The poor woman was greatly disturbed by the news that the certificates were probably valueless.

“How much did he owe you?” asked Frank.

“Three hundred dollars. Oh, I thought I was foolish when I didn’t insist on getting the money, but he said the certificates would be worth much more than the three hundred dollars and that he was giving them to me as a special favor.”

The knowledge that Pedro Vincenzo had paid his landlady in certificates of Rio Oil stock strengthened the Hardy boys in their suspicion that the lodger was connected in some way with the fraud case.

“I’d like to know more about that fellow,” said Frank when they left Mrs. Smith a little later. “I should particularly like to know where he went when he hired that big speedboat from Sandy MacPherson.”

“Perhaps if we take a run to the villages down the bay we may pick up some information,” Joe suggested.

“That’s not a bad idea. Let’s go and see if the boat is ready yet.”

On their way down to the waterfront the boys encountered Chet Morton and Tony Prito, an Italian lad who had been one of their chums for years.

“Tony and I,” announced Chet, “are looking hopefully for fun, trouble, adventure or whatever you have.”

“How about a spin in the Sleuth?” suggested Frank.

“Let’s go!” Tony said, his dark eyes fairly dancing.

Chet considered the matter.

“The proposal has its good points. But how long shall we be away from the home port? Shall we be back in time for dinner? The salt water always gives me an appetite and if I miss a meal I hate to think of the consequences. The shock to my stomach would be too much.”

“It wouldn’t hurt you to go on a diet for a few weeks anyway,” returned Tony unsympathetically. “You’re getting too fat.”

“We’ll bring along a picnic basket,” Joe suggested. “Then there’ll be no danger of having you die on our hands through starvation.”

“Now you’re talking! The voyage is on.”

The boys made up a substantial basket of lunch in the kitchen of the Hardy home, with Chet lending so much assistance that Aunt Gertrude finally chased him outside. He managed to scoop up a slab of pie on his way, however, so that the others found him whistling happily when they joined him a few minutes later.

Sandy MacPherson had done his work well, and the motorboat showed little evidence of the previous day’s accident when the boys inspected it at the boat-house. Frank and Joe questioned him, hoping that he might be able to give them a clue concerning the stranger’s destination when he rented the powerboat. But Sandy insisted that the man had told him nothing.

“I found this in the boat, if it’s of any interest to ye,” he said, taking a colored folder off a nearby shelf.

The moment Frank and Joe examined the sheet they realized that it might be an important clue. It was a time-table of the Coastal Air Transport Company, an aviation firm that had just constructed a new airport on the bank of the Willow River, some little distance down the bay.

“First port of call!” said Frank, and put the folder into his pocket. “We’ll see if the airport people know anything about him.”

The boys got into the boat, Chet carefully carrying the lunch basket, and in a few minutes the Sleuth was speeding down the bay. The day was clear and sunny, the water was calm. Chet busied himself trying to find a safe place for the lunch basket, which seemed to be his chief concern. He was still hunting for a satisfactory spot when Frank took a highly-colored document from his pocket.

“Like to buy some oil stock, Chet?” he asked.

Frank had persuaded Mrs. Smith to lend him one of the certificates Vincenzo had given her, in the hope that it might help him trace the Mexican.

“What have you there?” asked Chet, resting the lunch basket against the side of the boat.

“Rio Oil. One thousand shares. Good for starting the fire in the morning.”

“Let’s have a look.” Chet reached for the stock certificate.

Unfortunately, Joe chose that particular moment to alter the course of the motorboat. The craft swerved suddenly, Chet lurched off balance, lost his grip on the handle of the lunch basket, and staggered wildly.

“Look out!” he roared. “The lunch!”

He made a frantic grab for the basket as it slid overboard, and leaned far over the side with an anguished yell when he saw the appetizing food splash into the water. Then there was a louder yell, for Chet had leaned over too far. He went tumbling headlong into the waves.

Tony Prito and the Hardy boys whooped with laughter when they saw Chet’s sudden and inglorious tumble over the side. As the fat boy came popping to the surface, his eyes wide, his mouth open, he uttered a strangled yell.

“Help! Hey—come back, you fellows! I’m drowning.”

Joe was already swinging the boat around.

“You couldn’t sink if you tried,” jeered Tony Prito. “You’d float.”

Frank and Tony between them managed to haul the dripping Chet back into the boat. He was still clutching the stock certificate that he had taken from Frank’s hand just before he went overboard, but his chief grievance was that the lunch was gone.

“What are we going to do?” he wailed. “Every bit of food we had in the boat is now at the bottom of Barmet Bay. We’ll starve.”

“Why did you fling the basket overboard?” asked Joe innocently.

“Me!” howled Chet. “I flung it overboard? Are you crazy? Do you think I would throw the lunch basket into the water?”

Chet was in a bad state. The thought of the lost food seemed to worry him more than his soaked clothing. Joe, with a wide grin, steered the motorboat toward an island not far away. Chet would have to be dried out before they could go on to the airport.

“How about that stock certificate?” inquired Frank. “I hope it wasn’t damaged.”

“That lunch was worth a lot more than the stock certificate,” Chet howled. “Here I am, soaking wet and the food all gone, while you talk about stocks that aren’t worth the paper they’re printed on.”

Joe brought the boat in to the island, which was uninhabited, and they got out. In a short time they had a fire blazing, and Chet’s clothes were drying before the flames. He was all for returning to Bayport at once, but the others would not hear of it.

“You won’t starve before we get back from the airport,” Tony Prito assured him. “Get into your pants and let’s be on our way.”

Chet was in a better frame of mind after his garments were dried. When the trip was resumed, he actually managed to be cheerful.

“There might be a frankfurter stand at this airport,” he remarked.

The motorboat sped down the bay until the mouth of the Willow River came into view. Joe guided their craft into the stream, and in a few minutes the boys came in sight of the flags that marked the boundaries of the airport. There was a small dock, where they tied up their boat. Then they followed a path that brought them to a long, low building upon which was the sign: “Office—Coastal Air Transport Company.”

“Good!” exclaimed Frank. “This is the place we want.”

“I’d rather see a sign reading ‘Office—Hot Dog Company of America,’ ” said Chet plaintively.

An alert, keen-eyed man was writing at a desk when they went in. He glanced up.

“Hello, boys! What can I do for you?”

Joe nudged Frank.

“Do the talking,” he whispered.

Frank leaned on the counter.

“Did a man by the name of Pedro Vincenzo book passage on one of your planes within the past few days?”

The official wrinkled his brows, glanced at a book, then shook his head.

“No one by that name,” he replied.

“He was a Mexican,” said Frank.

“A Mexican, eh? Tall, swarthy, good-looking in a way——”

“That’s the man.”

“There was a chap of that description in here yesterday morning. But he didn’t book passage for himself. He wanted a ticket for another man.”

“Do you know that person’s name?” asked Joe, eagerly.

“He is registered here as Peter Smith. He was an elderly chap, as far as I can remember.”

A sudden droning that grew into a roar interrupted them. The airport official glanced at his watch.

“Crawford is just coming in now,” he said. “He is the pilot who made the flight. The foreign looking man booked passage to New York for a friend of his, but that’s all I can tell you. If you’re looking for information, maybe Crawford can help you.”

The Hardy boys thanked him and left the office. Chet Morton and Tony Prito were very curious.

“What’s it all about?” asked Tony. “Are you working on another mystery?”

“We don’t know yet,” Joe told him.

A big passenger plane was just settling to earth. Mechanics ran forward to take charge of the big machine. When the ship came to a stop the pilot clambered out, removing his helmet and goggles. He strode up toward the office.

“Are you Pilot Crawford?” asked Frank.

He grinned at them. “At your service!”

“The inspector has just told us that you took an elderly gentleman to New York. Would you mind giving us a description of him?”

Crawford laughed.

“I won’t forget him in a hurry,” he said. “I never saw such a nervous man in the air in all my life. It was his first flight and I think he was quite sure it was going to be his last.”

“Was his name Tremmer?”

The pilot shook his head.

“He didn’t tell me. He was a short, quiet little fellow—about fifty, I’d say. Wore horn-rimmed glasses, and had a gray mustache.”

Frank and Joe looked at each other. They knew Elmer Tremmer by sight, and the pilot’s description exactly fitted the missing bookkeeper.

“We’re rather interested in him,” Frank told the pilot. “Did he go to New York?”

“Yes, I landed him with my other passengers and he took off in another plane right away. A fellow met him——”

“Did you see the man who met him?”

“Yes. Foreign looking man. Black mustache and beard. But I’m afraid that’s all I can tell you.”

“You have helped us a lot,” Joe assured the pilot. He turned to Frank. “Let’s call up that New York airport.”

“Did he take a Coastal plane?” Frank asked Crawford.

“Sure. But I don’t know where he was headed for. Perhaps the officials in New York can tell you.”

As the boys hurried back to the office Chet remarked:

“I just love being a detective. What is this all about, anyway?”

“We don’t know ourselves,” Joe told him.

The Hardy boys put through a long distance call to the Coastal Air office at Roosevelt Field. The connection was soon completed and Frank asked if a passenger by the name of Peter Smith had been booked out the previous night.

“Just a moment, please.” Evidently the company’s filing system was efficient, for the information was soon forthcoming. “Mr. Smith is booked to Brownsville, Texas.”

“Thank you.”

Frank turned to his brother with a whistle of amazement.

“Brownsville, Texas!” he exclaimed. “Elmer Tremmer is traveling far and fast.”

Chet stared at him.

“The missing witness! Do you mean to tell me that you fellows have picked up Elmer Tremmer’s trail?”

Frank nodded.

“I think so. But it’s a trail that leads to Texas. And it’s all mixed up with a man who ran into our boat, and a hairless dog and a few oil certificates and a mark on a door.”

The Hardy boys were highly elated that their hunch had been correct. At least, they would have some valuable information for their father. They lost no time hastening back to the motorboat and making a quick run to Bayport.

“What’s the hurry?” Chet wanted to know. “If Tremmer is in Texas you’ll never be able to catch him.”

“As long as he is on United States territory Dad may be able to have him brought back. But if he ever gets across the border into Mexico it will make a big difference,” Frank pointed out. “There is no time to lose.”

When the boys returned home, however, they found that Fenton Hardy was out. Greatly disappointed, they waited impatiently for him. An hour passed before they heard their father’s familiar step in the hall. Frank and Joe rushed out to meet him.

“We’ve picked up Tremmer’s trail!”

“He’s flying to Texas!”

Fenton Hardy stepped quickly into his study and sat down at his desk.

“Really?” he asked. “Tell me about it.”

The boys hastily gave their story. Fenton Hardy was astounded.

“I can hardly believe it,” he said. “The man seems to have gone of his own free will. But why did he offer the authorities his help and then clear out just when he was needed?”

The boys’ father reached for the telephone and called the District Attorney. In a few words he acquainted that official with the news. After a brief conversation he replaced the receiver.

“We’re going to Texas!” said Fenton Hardy abruptly.

The boys stared at him. They were incredulous.

“We!” they cried.

Their father smiled.

“Don’t you want to go?”

“When do we start?” demanded Frank.

“Just as soon as we can. I think you boys deserve the trip, seeing you located Tremmer for me.”

Joe did a little step dance in the middle of the floor.

“But it will take two or three days to get to Texas, won’t it?” asked Frank. “By that time who knows where Tremmer will be?”

“He didn’t waste any time. Neither will we,” Mr. Hardy said. “We’re going by plane.”

The boys were almost speechless with excitement. They rushed madly from the room.

“We’ll be packed up and ready in five minutes,” shouted Joe.

Fenton Hardy was using the telephone again. He was calling the airport, inquiring about the flying schedule.

Frank and Joe were halfway up the stairs when the doorbell rang.

“Bother!” muttered Frank. “Just when we’re in a hurry.” However, he hastened downstairs and opened the door.

The visitor was Mrs. Smith, the erstwhile landlady of the mysterious Pedro Vincenzo.

“I hope I’m not troubling you, Frank,” the old lady said, “but I found something I thought you might like to see. It’s part of a letter that I discovered under the carpet in Mr. Vincenzo’s room. I can’t understand it myself. Besides, it’s partly burnt, but perhaps it will help you find the rascal.”

The Hardy boys were in a state of great excitement over the thrilling prospect of an airplane flight to Texas, and impatient to be on their way. But when Mrs. Smith stated the object of her visit they knew that it might have an important bearing on their own mission.

“Won’t you come in, Mrs. Smith?” Frank invited.

“No, thanks. I just brought this letter over in case you might be able to make use of it. I can’t make head nor tail of the thing myself.”

The landlady handed Frank a crumpled envelope with charred edges. Then, remarking that she had a great deal of work to do if her boarders were to have supper on time, she took her departure.

“What’s all this about a letter?” Fenton Hardy called out from his study.

The boys brought in the missive to him and told him about their investigations of the stranger known as Pedro Vincenzo.

Mr. Hardy was deeply interested, particularly as it was evident that the man was connected in some way with the Rio Oil Company and Elmer Tremmer’s disappearance.

“Let me see the letter,” he suggested.

Both the envelope and the page within had been badly burned; more than half the letter had been destroyed. When Frank carefully removed the charred sheet he saw that the message had been written in a foreign language.

Fenton Hardy examined it carefully.

“Spanish,” he remarked. “I used to know a little of it. Let me see—‘a rogue and a rascal. I have nothing but contempt for you and in answer to your impudent proposal that you marry my daughter Dolores I warn you that I shall never give my consent—’ And that seems to be all that’s left of the letter.”

“Is it addressed to Vincenzo?” Joe asked.

“Isn’t there a name signed to it?” said Frank.

“Both signature and address are missing. I’m afraid we can’t attach much importance to this document. However, keep it in your pocket. It may be useful some day.”

Mr. Hardy gave the letter back to Frank.

“The airport tells me that we can make connections with a night plane from a Jersey field if we leave here at seven o’clock,” he told the boys. “I’ve made the arrangements. We’ll travel light, and if we’re in the south for any length of time we can buy what extra clothing we need down there.”

For the next two hours the Hardy boys were in a frenzy of excitement as they prepared for the trip. Their mother was a little dubious when she was told of the projected journey, but as Fenton Hardy explained that the boys had really earned the trip by their clever detective work in tracing Elmer Tremmer, she gave her consent. Aunt Gertrude, however, was against the idea from the moment she heard of it.

“Airplanes!” she snorted. “Traveling by airplanes! Well, I may as well say good-bye to you now, for I’ll never see you again, not in this world. It’s bad enough to have the man of the house traipsin’ off halfway around the world without ten minutes’ warning, without the children going along, too.”

“Children!” exclaimed Joe indignantly.

Aunt Gertrude always treated her nephews as if they were still in rompers.

“Yes, children!” she answered. “Flying to Texas! Now in my day——”

Aunt Gertrude was off on one of her familiar monologues to the effect that in her day boys were much better behaved than they were in the present generation.

Finally, however, Fenton Hardy and his sons took their departure. They reached the airport by taxi in good time to take their places in the big passenger plane that was to carry them to the Jersey field. It was not their first experience in flying. Frank and Joe had been involved in some thrilling air adventures on a previous occasion when they solved the mystery of a series of mail thefts, described in “The Great Airport Mystery,” one of the earlier volumes of this series. But this was to be their first long flight, and they were agog with anticipation of adventures that might await them at the end of it. They were not destined to be disappointed. Stranger experiences than any they had ever had before lay in store for them.

The big night flying machine to which they transferred when they reached New Jersey was a revelation to the lads. It was a veritable liner of the air, a roomy, luxurious craft that carried them swiftly through the night, high above the scattered clumps of lights that marked the locations of towns and villages. Frank and Joe were so excited that they could not sleep. Their father, to whom air travel was an old story, settled himself comfortably and was soon slumbering peacefully.

The plane landed at a southern airport during the night. The boys got out to stretch their legs while the machine was checked and refuelled. Daybreak found them drumming steadily over the farm lands, lakes, rivers and valleys that lay far below in the first rays of the rising sun. The big craft was eating up the miles. Frank caught sight of a train in the distance. It looked like a toy, with a tiny line of white smoke streaming from the funnel of the locomotive. In a few minutes they had left it far behind them. Frank realized how hopelessly they would have been outdistanced by Tremmer should they have traveled by rail.

They changed to another plane that morning, and it was shortly after they took off on the fourth leg of their flight that they had their first taste of adventure. There were several other passengers; every seat was taken, and the baggage capacity of the ship was within a few pounds of the safety limit. The big machine lumbered down the field, taking off sluggishly, finally to gain altitude and roar off into the south.

“This machine doesn’t fly as smoothly as the others,” Frank remarked to his father.

“It’s carrying more weight, I suppose.”

However, it soon became evident that the pilot was having trouble. The tail of the ship dipped constantly. After a while the mechanic came back and conferred with the steward, who disappeared into the regions at the rear of the ship. The plane gave a sudden lurch, the nose went up sharply, and the Hardy boys glanced at each other in alarm. The pilot had his ship well in hand, however, and in a moment had it once again on an even course.

There was a sudden scuffle at the back of the passage, as the steward emerged, dragging by the collar a ragged, olive-skinned boy.

“A stowaway!” shouted Frank.

The steward’s face was flushed with anger. He shook his captive vigorously.

“How did you get in there?” he cried. “Don’t you know you might have caused a crash? We’re overweight. What’s your name? Where do you come from?”

The captive, who was about Frank’s age, merely shrugged his shoulders helplessly and shook his head as if to indicate that he didn’t understand.

“You understand me all right!” declared the steward angrily, wagging his finger under the youth’s nose. “What do you mean by stowing away in this ship? Speak up, boy!”

The lad refused to do so. He merely continued to shake his head, with an expression on his face which indicated he could not comprehend a word the steward was saying.

“We’ll attend to you at the next stop,” the steward declared. “If you can’t speak English we’ll find someone who knows your lingo.”

He made the boy sit on a small folding stool. There the stowaway crouched, his arms encircling his knees, looking all the while very wretched.

Darkness had fallen, and the gleaming lights of the airport that marked the end of their journey came in sight. The big plane swooped down, descended in a great spiral, and finally settled to the ground in a perfect landing. Then, with motor open, it taxied across the level field toward the hangars.

The steward was so busy attending to the passengers that for the moment it seemed he had forgotten about the stowaway. The youth got out of the plane close behind the Hardy boys but made no attempt to escape. He stood there, a lonely and dejected looking figure. Suddenly from out of the gloom there came a stranger. His face was obscured by the broad brim of his hat. He stepped up to Fenton Hardy and bowed politely.

“Señor Hardy?” he inquired in a low voice with a foreign accent.

Mr. Hardy was surprised.

“Yes,” he admitted. “How do you know my name?”

“Ah,” replied the man, “we have been expecting you. I have a message——”

With that he thrust a folded note into the detective’s hand, turned away, and vanished into the darkness.

There was a cry of alarm from the stowaway. He grabbed Frank’s arm.

“Don’t let him see me!” cried the boy. “Oh, don’t let that man see me!”

“So you can talk English?” remarked Frank.

Under the airport lights the Hardy boys could see that the stowaway’s face was white with fear.

“What’s the matter?” asked Joe.

“That man! I’m afraid of him. I’m glad he’s gone now.”

The stowaway still clung to Frank’s arm, as if in terror lest the stranger return.

“Well,” Frank remarked, “I must say that this is a queer sort of reception.”

“It is indeed,” said Fenton Hardy, who had been reading the note the foreigner had thrust into his hand. “We don’t seem to be welcome, if I’m to take this note seriously.” He turned to the stowaway. “You know that man?”

“Yes, Señor,” returned the boy in English which was perfect, but had a foreign accent. “I know him only too well.”

“Perhaps you had better come with us,” Fenton Hardy suggested. “I’d like to know something about the fellow myself.”

“What was in the note, Dad?” asked Frank.

“It might possibly be a practical joke, but I’m afraid it’s serious,” returned Mr. Hardy. “Listen——”

He read aloud the following extraordinary communication:

Joe whistled solemnly.

“That’s straight from the shoulder. We aren’t to go to Mexico, eh? But if Tremmer is still in Texas there will be no need of our crossing the border.”

Mr. Hardy shook his head.

“Our mission is known. This letter means that Tremmer is no longer in Texas.” He turned to the stowaway. “You say you know the man who gave me the letter?”

The boy nodded.

“His name is Señor Bario. I am very much afraid of him. He kidnaped me from my home.”

“Kidnaped you!” cried the Hardy boys in astonishment.

“It is the truth. I am trying to return to my home. That is why I hid myself in the airplane. If Señor Bario had discovered me, he would have kept me from reaching my home again.”

“Not while we’re around,” declared Joe confidently.

“He is a bad man, and he has helpers who are as wicked as he is.”

“What is your name, my boy?” asked Fenton Hardy.

“Juan Marcheta, Señor.”

“Then come with us to our hotel and let us hear more about this Señor Bario. Perhaps we can help you and perhaps you can help us.”

The Hardys got their baggage and climbed into a waiting taxi. The airport was on the outskirts of a thriving town that boasted a third-rate hotel. Mr. Hardy engaged connecting rooms for himself and the three boys. After they had eaten they settled down to listen to Juan Marcheta’s story. The boy, who devoured a tremendous meal, confessed that he had not eaten in twenty-four hours.

“You see,” he said, “I have come all the way from New York. For part of the way I begged rides on automobiles—what is it you say?—hitch-hiking. Then, when I saw my chance to hide in the airplane, I took the risk.”

“You are a Mexican?” inquired Mr. Hardy.

“Si, Señor! My home is in Mexico.”

“How did you happen to be in New York, so far away from home? You said something about being kidnaped.”

“It happened in this manner, Señor. There was a man by the name of Señor Pancho who came often to our hacienda. I have a sister, you understand, by the name of Dolores. She is very beautiful. Señor Pancho wished to pay respects to her but my father said he is not welcome. Ours is a very old family and we have an honored name, but this Pancho—bah—he is a low-caste fellow. He has money, yes, or so he said, but that matters not. One who marries my sister Dolores must be of her own station in life.”

“And what did Señor Pancho do when he was told that his attentions weren’t welcome?”

“He was very angry. He say that my father will regret it. Then he went away and we did not see him again. We were told that he had left the country. Nevertheless, I am sure that Señor Pancho had something to do with the kidnaping.”

“How did that happen?” asked Mr. Hardy.

“I was studying my lessons in the garden one afternoon when a man called to me from the gate. He say there had been an accident on the road and that his friend had been hurt. Of course, I went out to see if I could help him. No sooner had I stepped out of the gate than a blanket was thrown over my head and I was carried into an automobile. I was bound hand and foot and gagged.”

“What happened next?” asked Frank eagerly.

“We drove for many miles. They had taken the blanket from my head but they blindfolded me so that I could not see where I was going. Later I was carried into an airplane and we flew for a long time. After that I was taken into another automobile. The men gave me food and later on removed the bandage from my eyes. But they warned me that it would mean my death if I cry out or try to get help. That was when I first did see my abductors. And one of them was the man who met you at the airport.”

“Señor Bario?”

“One of his friends called him by that name. Well, to go on with my story. I was brought all the way to New York, and there I was turned over to three other Mexicanos who kept me a prisoner in their house. At first I did not make any attempt to escape, so gradually they became careless and one night I managed to flee through a basement window. A stranger offered me a ride in his automobile and I got out of the city. I have been making my way home ever since.”

“Do you know if anyone made a demand on your father for ransom?” asked Mr. Hardy.

“I do not know. The men, they told me nothing and answered none of my questions.”

“Perhaps that was Señor Pancho’s way of getting revenge,” Joe suggested.

“I am sure Señor Pancho had something to do with it,” returned Juan.

“You are still a long way from home,” Mr. Hardy reminded the boy.

Juan smiled. His predicament did not seem to cause him a great deal of anxiety.

“I have come so far,” he said. “A few hundred miles more, they will not matter.”

The Hardy boys laughed.

“You take it coolly, at any rate,” said Frank.

Mr. Hardy was strangely thoughtful. At last he turned to his sons.

“Mrs. Smith, the landlady, told you that Pedro Vincenzo used to talk about Mexico. He did not tell her his address, did he?”

“He said he came from a part of the country where people lived in caves.”

“Ah,” said Juan quickly. “Did he mention the Tarahumares?”

“Come to think of it,” said Joe, “it seems to me that Mrs. Smith was trying to get her tongue around a name like that. She called them Tarmars. What are they, Juan?”

“Indians,” returned the Mexican lad promptly. “The Tarahumare Indians live in the northern sierras, in the mountains of Chihuahua. There are caves in the Septentrion Cañon, of course, but people do not live there any more.”

“It’s a slim clue,” said Mr. Hardy, “but if Pedro Vincenzo comes from the mountains of Chihuahua he may have sent Tremmer there.”

“You are looking for someone?” asked Juan politely.

“Yes. And perhaps you may be able to help us. Do you know Mexico well?”

“I have traveled a great deal in my own country.”

“Could you guide me to this country of the Tarahumares?”

“I must return home first, of course. But with my father’s permission there is nothing I should like better than to help you.” Juan’s eyes sparkled with excitement. “It would be the sort of adventure I prefer.”

Fenton Hardy outlined briefly the story of Pedro Vincenzo and the missing witness, Elmer Tremmer.

“The man may still be in Texas,” he said. “Tomorrow I am going to make some investigations and try to pick up his trail. If I can’t find him I suppose our best plan is to go on into the Chihuahua country. At least,” he added, “I will go on into Mexico with you, Juan, and Frank and Joe can wait here until I return.”

Consternation was written in the faces of the Hardy boys.

“Do you mean to say we can’t go with you, Dad?” cried Frank.

Mr. Hardy shook his head.

“It’s too dangerous, I’m afraid. This may be just another wild-goose chase. You are safer on United States soil.”

The boys were keenly disappointed. Now that they had come so far it was a crushing blow to learn that they might have to sit cooling their heels while their father went on to further adventures in the romantic country across the Rio Grande.

“We won’t be any trouble, Dad,” pleaded Frank. “We can take care of ourselves. Besides, you may need us.”

“I don’t like to disappoint you, but it’s your safety of which I’m thinking. We’ll be going into pretty wild country, won’t we, Juan?”

“Very wild,” admitted the Mexican boy.

This, however, only increased the Hardy boys’ determination to accompany their father. Juan Marcheta, sympathizing with them, said:

“I must go home first. Why not let your sons come with us and stay at my place? They will be quite safe there and I know my parents will be glad to have them visit for a while. It is not far from the Chihuahua country and it will be more interesting for them than waiting here.”

“Well, I won’t promise,” said Fenton Hardy. “We’ll see about it tomorrow. Maybe we won’t have to go to Mexico at all. After we’ve all had a good sleep we can make further plans.”

Before the boys retired that night Frank said to his brother:

“I’ll be glad if we find Elmer Tremmer, all right, but I hope he went to Mexico.”

“So do I,” said Joe. “A chance like this comes only once in a lifetime.”

Fenton Hardy was up early next morning and left the hotel immediately after breakfast. He announced that he was going to make a determined effort to pick up some information about the missing Elmer Trimmer.

“In the meantime,” said Frank, “we’ll see if we can locate Señor Bario.”

The lads amused themselves by exploring the town that morning. Occasionally Juan Marcheta would question some of his own countrymen. He found no one, however, who knew Bario.

“I noticed that he got into a blue roadster after he gave Dad the warning last night,” Joe said after a time. “I think I would recognize the car if I saw it again.”

“I can’t understand how Bario comes to be mixed up in our case,” Frank declared. “He is a kidnaper, not an oil swindler.”

“He may be both,” said Juan. “Who knows?”

“Bario must be connected with Vincenzo’s crowd and we must be on the right trail or he wouldn’t have tried to frighten us into staying out of Mexico, that’s certain. I wonder if he really thought that letter would throw a scare into us?”

Juan Marcheta shook his head dubiously.

“Such men will stop at nothing,” he said. “You are taking a great risk.”

“That’s what we’re here for,” remarked Joe cheerfully. “Let’s make the rounds of the garages and parking places and look for that machine.”

They viewed scores of autos within the next hour, and found several blue roadsters. Joe could identify none of them as the machine in which Bario had driven away from the airport the previous night. When it was nearly noon Frank suggested that they give up the search and resume it after lunch.

“Just a minute!” exclaimed Joe, as they passed the entrance to a narrow lane. “That looks like it.”

A battered looking blue car was parked in the pathway, and Joe ran down to inspect it. He came back in a few minutes, jubilant.

“Same roadster!” he declared. “I’d know it anywhere.”

“Then we’ll just wait here until Bario comes out,” said Frank.

“I have a better plan than that. He might drive away before we can stop him. I’m going to hide in the rumbleseat. Then I can’t possibly lose him.”

Juan Marcheta, fresh from his experience at the hands of the kidnapers, thought Joe’s plan was risky and advised caution, which Joe, however, would not listen to.

“For all we know, Tremmer might be right here in town. If he is, then Bario is very likely in touch with him. I might solve this whole case single-handed.”

With the greatest confidence in the world, Joe went back down the lane and vanished into the rumbleseat of the roadster.

Frank and Juan waited at the mouth of the alley. They were fully prepared for a long stay, but in a few minutes a door opened and two men hurried out of one of the buildings in the lane. They got into the car, which lurched forward, and then shot out into the street, disappearing down the road in a cloud of dust.

The two boys gave chase but the auto swerved around the next corner. By the time Frank and Juan reached the intersection the roadster was nowhere to be seen.

“I hope Joe is enjoying the ride,” said Frank, trying to disguise his anxiety. “They may take him all the way to Mexico.”

“It was a foolish thing to do,” Juan remarked gravely.

They hurried down the street, with very little hope of seeing the car again. Then ten minutes later, in the business section of the town, they were greatly elated to see the blue roadster standing in front of a barber shop. On the sidewalk, engaged in conversation with the two men who had driven the car away, stood Joe Hardy.

“They caught my brother!” declared Frank. “Let’s hurry.”

However, when Juan and Frank came up to the trio in front of the barber shop, they were relieved to see that Joe was in no trouble, but was talking to the strangers on apparently friendly terms. A moment later the men went into the shop and Joe trudged toward his companions with a pleased grin on his face.

“I thought I was in for it that time,” he laughed. “The car hit a bump and I let a yell out of me when I hit my head, so the men knew they were carrying an extra passenger.”

“How on earth did you get out of that scrape?” asked Frank.

“They fished me out when the car stopped. They wanted to know why I was riding in the rumbleseat, so I simply told them the truth. They were Americans and I explained that I thought the car belonged to Señor Bario because I had seen him driving it last night. But the car didn’t belong to Bario at all. One of those men is a barber and it’s his car. He says Bario ‘borrowed’ it from him last night without permission, and that he would have the fellow arrested if he could find him. But he can’t find him.”

“Why not?” asked Juan.

“He turned the case over to the police, and now it seems that Bario has left town. I tell you, that little car drive was worth while. I picked up more information in those five minutes than we learned all morning. And here’s the important part,” said Joe, evidently saving the best for the last. “Tremmer was with Bario!”

“Tremmer!” exclaimed Frank.

“The same gentleman. The barber told me that Bario came into the shop yesterday with a little near-sighted man who wanted his mustache shaved off. Bario called him ‘Señor Smith.’ So there you are. And the police say Bario and this Señor Smith left town together.”

Joe was very proud of himself, as he had good reason to be, and suggested that they all hurry back to the hotel at once.

“I think we’re going to take a trip to Mexico,” he said.

Fenton Hardy was waiting for the boys. He had not, it appeared, succeeded in acquiring much information about Elmer Tremmer.

“The airport people tell me he landed here all right. He came on from Brownsville yesterday morning, but seems to have disappeared into thin air.”

“With Señor Bario,” said Joe calmly. “They cleared out together.”

Fenton Hardy looked at his son in surprise.

“How do you know?”

“We’ve been doing a little detective work ourselves.”

Joe then told his father about the blue roadster and the information he had gleaned from the barber. Mr. Hardy knew the ability of his sons so well, that he was not exactly surprised, though highly pleased, at Joe’s success.

“That settles it, then,” he declared. “The trail of Bario is the trail of Tremmer—and it leads to Mexico.”

“And we may go with you?” asked Frank anxiously.

“I can’t very well refuse now,” said Mr. Hardy with a smile. Then he turned to Juan Marcheta. “We’ll take you home, of course, Juan, and you can help us locate this country of the cave dwellers. If that doesn’t work we’ll investigate the district where the Rio Oil people were supposed to have their wells.”

“When do we leave—and how?” asked Frank.

“We’ll leave tonight, if I can make arrangements for an airplane. I think it would be best if we should leave quietly. Bario may have friends in town and you may depend upon it that they’ll be watching us.”

That afternoon Mr. Hardy found a free-lance pilot who was willing to fly them across the border and to whom he explained the situation. The aviator suggested that the detective and his party drive out of town after darkness had fallen, promising to pick them up at a lonely place about twenty miles away.

Late that night a taxi was waiting at a side door of the hotel. Fenton Hardy and his sons, accompanied by Juan Marcheta, slipped quietly out and got into the car. They gave the driver his directions, and the taxi pulled away from the curb.

“All these precautions may be unnecessary, but it’s well to be on the safe side,” Mr. Hardy remarked. “Bario knew of our arrival, and it’s probable that he will have someone checking up on us.”

Frank glanced out the rear window of the taxicab.

“There’s a car following us,” he said.

Mr. Hardy spoke to the driver, who promptly turned down a side street, sped up a narrow lane, raced down another street, and performed a variety of intricate maneuvres designed to throw any pursuers off their trail. But when they reached the road leading out of town they could still see the headlights of the car behind.

“So!” remarked the chauffeur. “Well, if he wants a race, that’s just what he is going to get. Hold tight!”

He stepped on the accelerator, and the taxi leaped ahead. For the next ten minutes the boys enjoyed one of the most exciting rides of their lives. The car leaped and pitched, took curves on two wheels, and roared on into the night at top speed. More than once it seemed that only sheer luck saved it from going into the ditch. The driver was an expert, however, and he knew just what his car would do. Frank, hanging on for dear life and gazing out the rear window, finally reported that the lights of the pursuing car had disappeared.

“I hope he busted an axle,” grunted the man at the wheel, slowing down to a more moderate rate of speed.

The headlights shone upon a vast expanse of treeless ranch land. The night was clear, with a full moon and a starlit sky. They drove on until they came to a group of deserted buildings beside the road.

“The old Bar-K ranchhouse,” said the driver. “Here’s where you stop.”

“Has the ranch been abandoned?” asked Mr. Hardy.

“Not a bit of it. Plenty of cattle on the Bar-K range yet. The new buildings are about five miles away.”

They got out of the car and Mr. Hardy paid for the trip. The man touched his cap.

“Thanks, mister,” he said. “I’ll remember what you told me. Nobody will get any information out of me. I say nothin’, hear nothin’ and see nothin’.” He glanced up at the sky. “It’s a good clear night. I guess your pilot will be able to pick you up without any trouble.”

“I hope so,” said Fenton Hardy.

The taxi driver swung his car around, bade them a cheery goodnight, and rattled off into the gloom.

It was an eerie and lonely place. Not a sound broke the deep silence. The deserted ranch buildings looked ghostly. The boys glanced up into the sky, but the plane was not yet in evidence.

“We may have to wait a while,” observed Mr. Hardy, “but the pilot said he would pick us up here without fail.”

“It will be a good joke on us if he doesn’t show up,” Joe said. “I don’t relish the idea of legging it back to town.”

In the distance the boys heard a faint rumbling sound. It came from beyond a dark slope at the back of the ranch buildings. They looked at one another, puzzled.

Juan Marcheta suddenly flung himself down in the grass and put his ear to the ground. He listened for a moment, his face serious. The heavy rumbling became louder. Juan leaped to his feet.

“It is no train!” he cried. “Quick! Run to the ranch buildings. There is no time to lose. They will be here in a minute.”

He dashed across the open ground toward the tumbledown ranchhouse.

“What’s the matter?” demanded Joe.

“Quick!” urged Juan. “Quick, or we’ll be trampled to death. I know that sound. Cattle! A herd of cattle on the stampede.”

The words had hardly left his mouth before the Hardy boys saw a wave of dark shapes break over the crest of the ridge. Hundreds of milling animals rushed madly toward them.

Fenton Hardy and the boys were about a hundred yards from the buildings when Juan cried his warning. The top of the slope was nearly a quarter of a mile away. Yet, as they broke into a run and sprinted for safety, they knew that it would be only a matter of moments before the great herd would reach the foot of the slope.

“If we’re caught out in the open we’ll be killed!” yelled Juan.

By this time the others needed no further urging. They could see the black mass of cattle pouring down the hillside, horns tossing in the moonlight, hoofs drumming on the earth. Any living object in the path of that mad stampede would be trampled to a pulp. The front ranks were now halfway down the slope, and still more were pounding over the crest of the hill. It seemed as if the cattle would rush relentlessly into the ranch buildings. For a moment Frank and Joe doubted Juan’s wisdom.

The group reached the shadow of the ranchhouse just as the stampede got to the foot of the slope with a thunderous roar. Juan and Joe, in the lead, raced across the few intervening yards of ground and flung themselves into an open doorway.

Fenton Hardy, thinking of the safety of his boys, had lagged behind, waiting to see that all gained the refuge of the buildings before he himself took to cover. It was well that he had done so. Just as he ran into the shadows Frank uttered a cry, stumbled and fell. At the same moment there was a crash and a splintering of shattered boards. Some of the cattle had plunged into a small fence at the back of the ranchhouse and carried it away in their headlong rush.

“All right, Son,” said Fenton Hardy, reaching down and grabbing Frank’s outstretched hand. “Are you hurt?”

The boy struggled to his feet. He tried to run but nearly fell again. His ankle had been twisted by the sudden tumble.

“Go ahead, Dad!” he gasped. “I’ll—make it—all right——”

“Nonsense!” Mr. Hardy flung his arm around Frank’s waist. He half dragged, half carried the lad toward the doorway. He was still in the danger zone as half a dozen steers came plunging around the side of the ranchhouse, bellowing madly. Frank and his father made one last desperate effort. One of the animals thundered toward them.

Fenton Hardy snatched off his hat and brandished it in front of the steer, which shied violently to one side, so close that its heavy flank brushed against Frank and knocked him down. The other animals went rushing past and a moment later Mr. Hardy had dragged his son to the safety of the doorway.

Juan Marcheta and Joe were limp with relief.

“I thought you were both done for!” said the latter.

“It was a very narrow—what you call it?—squeak!” said Juan.

“Close enough,” remarked Mr. Hardy. “How is your ankle, Frank?”

“It will be all right. When that steer hit me it felt as if I was being grazed by a locomotive.”

The boy managed to get to his feet, and the group stood in the doorway watching the awe-inspiring spectacle. Hundreds of cattle were milling about in the moonlight, and hundreds more were still thundering down the slope behind the ranchhouse.

Suddenly, in the clear night sky, the Hardys saw a winged object skimming high overhead.

“The plane!” cried Joe.

Their pilot had kept his appointment!

It was obvious, however, that it was impossible for him to make a landing. The waiting travelers saw the machine circling above the ranch buildings. Mr. Hardy took a flashlight from his pocket, aimed it skyward, and flashed a signal. A moment later the riding lights of the plane blinked off and on.

“He knows we’re here, at any rate,” Frank said.

As the aircraft swung around in another circle, the boys caught sight of an object sailing through the air. It struck the roof with a dull thud, bounced off, then fell to the ground. It proved to be a white handkerchief tied around a small bolt. When Juan retrieved it, he found that the piece of linen contained a scribbled note.

“Can’t land here. If you can get away and meet me a mile up the road, flash once. If you can’t get out, flash twice.”

“We certainly can’t get out while the cattle are here,” said Juan.

Although the stampede had ended, the animals were now herding up around the old ranch buildings. Mr. Hardy raised the flashlight and signaled twice. A moment later the plane straightened out and droned off westward. Then it turned, and came swooping down at terrific speed close to the ground, its motor wide open.

The cattle bellowed with fear. As the roaring monster of the sky swooped toward them, not fifty feet from the earth, the steers suddenly broke and fled. In a moment the earth was again echoing to the thunderous trample of hoofs. The plane banked sharply, for the pilot did not want to get too far above the herd and turn them back again. He swung around to the rear of the living mass and came speeding ahead once more. In less than a minute the animals, routed, plunged back up the slope. When the last of them had vanished over the top of the ridge, the airplane settled down to earth, bumped heavily, righted itself, and came to a stop.

Fenton Hardy and the boys hastened out of the deserted building that had been such a providential refuge. Their pilot, a bronzed, weatherbeaten young man, stood waiting for them.

“That’s the first time I’ve ever tried riding herd from the air,” he remarked. “I didn’t expect it would work, but I thought I’d try it anyway.”

“It worked, sure enough,” said Joe. “I’ll bet they won’t come back this way in a hurry.”

The travelers took their places. In a few moments the idling motor again broke into a roar, the plane went rolling over the level field, took off, and climbed steadily into the sky. Frank and Joe were tense with excitement. As the nose of the ship turned southward they gazed toward the stars shining above the mysterious horizon.

“On to Mexico!” shouted Frank.

The flight itself was uneventful. The boys experienced a thrill when they flew over the Rio Grande, the great river shining like silver in the moonlight, and realized that they were at last over foreign soil. The plane landed on the outskirts of a small town shortly after daybreak and refuelled, then took off at once on the second leg of its journey.

Within a few hours Juan began to show signs of excitement, evidently recognizing country that was familiar to him. It was all strange and wonderful to Frank and Joe.

The voyagers passed over a great desert where millions of acres of sand lay beneath the sun, broken here and there by marshes, lakes and buttes of reddish rock. Then the aridity gave way to subtropical vegetation and high towering hills, with great gorges through which tumbled mountain streams. Finally they approached the foothills of the sierras, and in the distance lay a city.

This was their destination! It seemed only a few minutes from the time the metropolis appeared in view that the plane was bumping to a stop in a field on the outskirts.

Now that his long adventure was at an end, Juan was impatient to get home. He could scarcely wait while Mr. Hardy gave instructions to the pilot, and Frank went away to find a taxi. When the four finally drove through the sunlit streets, Juan was as excited as a child.

“Soon I shall be home!” he exclaimed in delight. “You shall meet my father, my mother and my sister Dolores. Ah! There is the wall of our hacienda. I can see the roof. The big trees. Drive faster—faster——”

He had the door open, and was out of the car before it stopped.

“Hi, Rafael!” he called to a sleepy looking servant near the gate.

Then followed a torrential command in his own language, which brought the astonished man over to take charge of the luggage. Juan grabbed Frank and Joe each by an arm.

“Come! You are my guests,” he cried. “Come, Señor Hardy. Oh, I am so glad to be home.”

There was tremendous excitement when Juan reached the great, shady hacienda beyond the wall. A tall, sunburned gentleman with white mustaches and a goatee leaped up from a chair on the veranda, cast aside his newspaper, and rushed at Juan with an incredulous cry of joy. A stout, handsome, dark-haired woman flung open the door, gazed at Juan as if he were a ghost, then burst into tears while she hugged him affectionately. A moment later a beautiful young girl in a white dress came running down the garden path.

“Juan!” she cried joyously, and threw her arms about him.

There was so much tumult and rejoicing that no one paid any attention to Fenton Hardy and his sons until at last Señor Marcheta turned toward them. His expression, however, did not indicate that he welcomed them with enthusiasm.

He made a stiff little bow.

“You will pardon me, Señors,” he said. “You will understand that it will be impossible for me to offer you the hospitality of my home, after what you have done. Will you please oblige me by leaving at once?”

He beckoned to the Mexican servant coming up the walk with the luggage.

“Rafael! Show these people to the gate.”

Fenton Hardy and the boys were amused as well as embarrassed. It was evident that Juan’s father took it for granted that they were in some way connected with the kidnapers. However, Juan himself soon cleared up the mistake.

“You are wrong, Father!” he cried. “These are my friends. If it had not been for them, I would not be at home with you now. They have been very good to me.”

Señor Marcheta became very agitated, bowed profoundly, and broke into a torrent of apologies. Juan, in his own language, explained to his mother and sister. Frank and Joe were astonished to hear the names “Dolores” and “Pedro” repeated several times in the voluble conversation. The close association of the two words recalled to them the partly destroyed letter that had been found in Pedro Vincenzo’s room, back in faraway Bayport.

When the Marchetas had heard Juan’s story, their demeanors underwent a distinct change. The father apologized again and again for his mistake, and warmly thanked Mr. Hardy and the boys for all they had done for his son.

“You will stay with us?” he begged earnestly. “You will do us the kindness of accepting our hospitality while you are in Mexico?”

Mr. Hardy explained that they were in the country on confidential business that might take them far afield. For the present, however, he gratefully accepted the offer. The servant Rafael was instantly ordered to carry the luggage into the house.

Juan told the story of his abduction, explaining how he had escaped from his captors in New York and had started back to Mexico alone. It was soon evident that Señor Marcheta was very proud of his son’s initiative and courage. As for the abductors, he vowed that he would some day bring them to justice.

“I was right!” he exclaimed. “Pedro Pancho is a rascal. Dolores,” he said to his daughter, “I was wise when I forbade him to come here.”

“Is this Pedro Pancho known by another name?” asked Frank.

“It is possible,” said Señor Marcheta. “He wished to pay court to my daughter, but it came to my ears that he had been mixed up in dishonest dealings above the border. He is an unscrupulous rogue, and I should not be surprised to hear that he called himself by another name.”

“Vincenzo, for instance?” suggested Joe.

The Marchetas knew Pedro Pancho only by the title under which he had appeared at their home. Frank took the partly burned letter from his pocket and handed it over to Señor Marcheta.

“Perhaps that is in your handwriting,” he remarked.

The Mexican examined the missive. As he did so, his eyes widened, and he gasped in astonishment.

“But this is magic!” he exclaimed. “How did you come by this? You arrive here from the United States, you are strangers, you have never met me before—and you hand me a letter in my own writing!”

“It is yours, then?” demanded Mr. Hardy eagerly.

“Indeed it is. I wrote this letter to that rascal Pedro Pancho.”

“I thought so,” said Frank. “I think there is no doubt but that Pedro Pancho and Pedro Vincenzo are one and the same person.”

“This is all very strange,” observed Juan’s mother, mystified. “Where did you find that letter?”

“Please tell us,” begged Dolores.

Fenton Hardy, however, seldom confided in anyone when he was working on a case. Now he explained politely that he was a detective and that while his business in Mexico concerned Pedro Vincenzo, or Pancho, it was of a confidential nature.

“Perhaps we can tell you the whole story after I have located this fellow Pedro,” he said.

“I shall be glad to help you,” declared Señor Marcheta. “It is possible that he may be bold enough to come here.”

It was arranged that the Hardys make the Marcheta home their headquarters while in Mexico, and that for the time being Frank and Joe remain for a visit with Juan. Mr. Hardy explained that he himself wished to run down certain clues that would take him away on a short flying trip. This would not last more than two or three days at the most, however.

“Come,” said Juan to the Hardy boys, “you must wash and change after your journey. Then I will show you about the grounds.”

Señor Marcheta was evidently wealthy, for the big house was luxuriously furnished. The room to which Frank and Joe were assigned was one of the finest they had ever seen. Juan let them use cool linen suits from his own substantial wardrobe until the Hardys should be able to purchase new clothes of their own. As all the boys were almost of a size, there was no trouble about the fit. Juan was plainly delighted that his new acquaintances were to remain for a visit and left nothing undone to add to their comfort.

Mr. Hardy remained at the Marcheta home that night, but left early the following morning. The boys might have felt disappointed in being left behind, had not the warm hospitality of the Marchetas done much to make them forget the adventures they might be missing. Besides, they planned to do a little detective work on their own account.

A few hours after their father’s departure Frank and Joe began to explore the grounds, delighting in the well-kept garden with its plants and flowers that were so strange to Northern eyes. At the back of the house they came upon a small doorway, partly hidden by vines and creepers. Here they made an astonishing discovery.

In the woodwork of the door was branded a familiar symbol—the letter P in a fire of blazing fagots!

The Hardy boys were utterly astounded. They could scarcely believe their eyes as they gazed at that sinister mark.

“Why, it’s the same one!” gasped Joe. “The same mark we saw on the door of Vincenzo’s room in Bayport.”

“It can’t be!”

They went closer and examined the peculiar symbol. In every detail it was identical with the branded sign they had seen before.

“Perhaps it’s been here for a long time,” Frank suggested. “Run and find Juan. We’ll ask him.”

When Joe brought the Mexican lad to the scene a few minutes later, the latter was quite as surprised as were the Hardy boys.

“I have never seen it before,” he said. “What does it mean?”

“I’m sure it means that Pedro Vincenzo has been here,” said Frank, without offering any further explanation. “Do you think the mark might have been placed here while you were away?”

“It is the door of the servants’ entrance. Rafael will know.”

Rafael, the domestic who had met them at the gate the previous day, was promptly summoned. When he saw the symbol, his eyes grew round with amazement. He spoke rapidly to Juan in his own language.

“He says the mark was not there last night,” Juan interpreted.

Frank and Joe did not want to alarm the Marchetas unduly, so they said nothing more about Pedro Vincenzo and his possible connection with the strange figure on the door.

“May have been somebody playing a practical joke,” remarked Frank.

“It may be a sign to ward off evil spirits,” Juan suggested doubtfully. “Perhaps I should tell my father.”

The Hardy boys dissuaded him from this course, however. They managed to distract Juan’s attention to some other topic. Later, however, they discussed the matter alone and agreed that the mark could have but one meaning. Either Pedro Vincenzo or some member of a possible gang of his had been on the grounds of the Marcheta home within the past twelve hours.

“It may not have been Pedro,” Frank pointed out. “The mark may be the symbol of a band. Just the same, it means that we’ll have to keep our eyes open.”

“Perhaps one of the servants is in league with him.”

“That’s what we’ll have to find out. We’ll keep a watch on the place tonight.”

“Perhaps we ought to tell Señor Marcheta after all,” Joe suggested.

Frank thought, however, that it might only cause their kindly host unnecessary alarm. Then, too, if any servants should be involved, he would be sure to know of any action that the Hardys might take.

“If Pedro Vincenzo has been here and there is any chance that he will be back, we want to take him by surprise if we can,” Frank said. “After dark tonight we’ll go out quietly and stand guard.”

Long after the Marcheta family retired that night two shadowy figures stole silently down the great staircase of the hacienda. Frank and Joe made not the slightest sound as they let themselves carefully out the front door into the velvety darkness.

“You watch the main gate,” Frank whispered to his brother. “I’ll keep an eye on the servants’ entrance.”

Joe disappeared into the gloom of the garden and made his way toward the gate. Frank flitted around the side of the house like a ghost, stole through the garden, and worked his way through the grounds until he came in sight of the door where they had found the strange and sinister mark. Behind a heavy clump of bushes he halted, and sat down to watch.

Long minutes passed. Beyond the wall Frank could hear the faint noises of the city. But the garden itself was wrapped in silence. The heavy perfume of flowers pervaded the darkness.

At length he heard a rustle among the trees. Across a patch of moonlight there stole a dark figure. Frank’s heart beat rapidly with excitement as he saw that the intruder was moving quickly toward the door.

It might be only one of the servants returning late, he reflected. However, there was something so stealthy in the man’s demeanor that Frank quickly discarded that notion. The man was enveloped in a dark cloak and wore a huge, broad-brimmed hat that hid his face from view.

Furtively the intruder glided up toward the door. He turned, looked from side to side, and groped beneath his cloak. The moonlight shone full upon his face for a moment.

Frank stifled an involuntary cry.

It was Pedro Vincenzo!

A second later the face vanished as the man crouched down in front of the door. Frank heard the rasp of a key in the lock.

The boy got cautiously to his feet. One of the bushes rustled, and he saw Vincenzo wheel about with a muttered exclamation and stare intently in the lad’s direction.

Frank remained perfectly still. Apparently the man did not see him concealed by the shadows at the side of the house. Vincenzo turned again and once more tried the key in the lock.

Silently Frank moved out from behind the bush and crept slowly closer. When he was within a few feet of the intruder he suddenly rushed and leaped upon Vincenzo before the man realized what was happening. There was a frightened yell as the boy bore him to the ground. The intruder struggled furiously, trying to break free of Frank’s grasp. He was a big man and very strong, but young Hardy had the advantage of taking him by surprise. He locked both arms tightly around Vincenzo’s neck and hung on.

“Joe!” he shouted. “Come quick, Joe! I have him!”

Vincenzo struggled madly, trying to shake Frank lose as the two wrestled back and forth on the gravel walk. Frank heard an answering cry from Joe, and shouts of alarm from within the house.

Then suddenly a dark figure plunged swiftly out from the bushes.

Frank had one glimpse of his attacker, but he was powerless to save himself. An arm rose and fell. A heavy object descended sharply on Frank’s head. He felt himself tumbling limply to the ground. Then he knew no more.

Pedro Vincenzo and the other man rushed off into the darkness.

Joe, who came running through the garden a few moments later, found his brother lying unconscious in front of the servants’ entrance.

“Frank!” he cried wildly, kneeling down beside the prostrate figure. “Frank! You are hurt!”

A door crashed open nearby. Then Señor Marcheta came running out, clad in pajamas and a dressing gown.

“What is it?” he cried in alarm. “What has happened?”

Frank stirred and opened his eyes.

“Pedro!” he whispered. “Don’t let him get away. He came to the door—I tackled him—someone knocked me out——”

“Pedro?” shouted Señor Marcheta.

In a moment he was summoning the servants, organizing a general search of the grounds.

Frank was carried into the house where Juan and Dolores helped Joe attend to his injuries. He had been struck a violent blow on the head, which had stunned him for a while. Beyond that, he was not seriously hurt, fortunately.

Lights were flashing in the garden as Marcheta and his servants made a thorough search for the intruders. When Señor Marcheta tramped into the house ten minutes later, he admitted that the miscreants had made good their escape.

“You are sure it was Pedro Pancho?” he asked Frank. “He dared to come here?”

“It was Pedro Vincenzo. I saw his face. Pedro Vincenzo and Pedro Pancho are one and the same, I think. He was trying to unlock the door.”

“But how does it happen that you were there?” demanded Juan in bewilderment.

Frank and Joe then explained how they had decided to keep watch on the house after they saw the strange sign on the door. The Marchetas were greatly disturbed.

“I shall send word to the police of the city tomorrow,” declared Señor Marcheta. “If Pedro Pancho is in the neighborhood he will be arrested.”

“I’m afraid the police will have a hard time catching him now,” Frank said. “He knows that I recognized him. He won’t dare stay around here.”

Frank’s assumption was evidently correct. Although Señor Marcheta used his influence with the police department the following day, and the whole city was searched, the officials could find no trace of their man.

The affair proved, however, that Pedro Pancho, alias Vincenzo, was actually in Mexico. Why he had attempted to enter the Marcheta home was explained in various ways. He might have been making a second attempt to abduct Juan. He might have intended to harm the Hardy boys. Or he might have planned to avenge himself upon the Marcheta family by setting fire to the house. One thing, however, was certain. There would be danger as long as the man remained at large.

“I must not allow you out of my sight from now on,” Señor Marcheta said gravely to Juan and the Hardy boys. “I have asked the police to guard my home at night. I have no further fear of danger from that source. But I think it would be best if we could go away for a little journey.”

“That’s a good idea!” declared Juan enthusiastically. “It will be dull for them if we stay at home. Perhaps there is some part of the country you would like to see?” he queried, turning to the Hardy boys.

Frank took from his pocket the elaborately engraved certificate of Rio Oil stock that Pedro Vincenzo had given the landlady in payment for his board bill. It had a highly-colored picture of an oil well, together with a paragraph purporting to give the location of the Rio property.

“This is a company that we’re—we’re interested in to some extent,” he said. “We’d like to see their property. Is it far from here?”

Señor Marcheta examined the fake security closely.

“I have never heard of the Rio Oil Company,” he said. “According to this certificate, their property must be located about two days’ journey from here. Ah, yes, the name of the village is written here. Would you care to go there?”

The Hardy boys said they would be glad to make the trip. In the back of their minds lay the hope that at the Rio Oil Company property they might pick up some information about Vincenzo and Elmer Tremmer.

“Then,” declared Señor Marcheta, “we shall set out early tomorrow morning. Perhaps your father will be back by that time.”

Fenton Hardy had not returned by the following day, however. Instead, there came a letter in his handwriting, and mailed from some obscure town in the mountains, stating that his return would be delayed for at least a week. The boys were curious as to the reason for his being held up. It occurred to Frank that the letter might be a hoax. A close inspection of the handwriting, however, persuaded them that the missive was indeed from Fenton Hardy.

“In that case,” said Juan, “there is no need to wait. We can leave without delay.”

Frank and Joe could not help but think, as they set off on their journey, mounted on horses from Señor Marcheta’s stables, that their chums back in Bayport would have been envious if they could have seen them. Clad in the costume of the country, with wide-brimmed sombreros to shade their eyes from the sun, they jogged along picturesque country roads through subtropical hills and valleys riotous with vegetation, stopping here and there at quaint little inns along the way. The boys had an opportunity of seeing the real beauty of Mexico, and many of their former ideas of the country were changed completely.

“I always had a notion it was just a big, sunburnt desert!” said Joe. “Nothing but cactus plants and bandits.”

Juan laughed.

“Mexico has much beauty,” he said. “There are mountains, and cañons, and jungles, and cities, and towns. The Tamasopa Cañon is one of the most beautiful places in the world. It is on the way from Tampico to San Luis Potosi. You cannot find such color anywhere else on earth. Millions of flowers grow there—cape jasmine, wild gardenias and orchids. Then there are the butterflies and the tropical birds. But of course we have deserts, too. We are going toward the desert called the Bolson de Mapimi. It was at one time a great lake. The bones of mastodons and other animals that lived millions of years ago have been found there. That is why the people of Coahuila call the place the Llano de los Gigantes, the desert of giants.”

Then Juan broke into a merry laugh.

“I sound like a school teacher,” he said. “Yet you shall see for yourselves. That is much better than to be told.”

On the second day of their journey the boys began to leave the fertile country behind. Juan told them that they were drawing closer to the desert. Señor Marcheta had made inquiries at the inn where they had spent the night, and informed Frank and Joe that they must not be disappointed if they found no oil wells in the neighborhood to which they were going.

“This is not oil country,” he said. “No one to whom I have spoken has heard of this Rio company you mention.”

“We won’t be surprised to learn that the Rio outfit hasn’t any oil wells,” Frank admitted.

When the travelers finally reached the village that had been indicated on the oil certificate, they learned that their suspicions had been correct. An innkeeper with whom Señor Marcheta conferred said that no oil had ever been found within many miles of the place, and that no such company as the Rio Oil Company had ever been heard of in the vicinity.

The innkeeper, a stout, swarthy fellow with a good-natured face, served the group a meal. Thereupon he went over and whispered confidentially to Señor Marcheta. Their conversation lasted for some time. When the man returned to the kitchen Señor Marcheta said:

“Perhaps there may be something to this Rio company after all. The man tells me that there are rumors in town about a place called ‘Headquarters,’ run by some shady characters who come here occasionally. It is out in the desert—an oasis, the innkeeper says.”

“We’re not going to turn back now,” Juan declared. “What do you say, Frank and Joe? Shall we strike on to this oasis, or ‘Headquarters,’ as they call it?”

The Hardy boys needed no urging. Even if Pedro Vincenzo had not taken flight to this part of the country, they were determined to see the desert at all costs. Señor Marcheta, smiling, agreed to continue the journey the following morning.

Eager with anticipation the Hardy boys had their first experience of the desert the next day. For miles and miles, stretching out to the distant horizon, lay wastes of golden sand in smooth hillocks and slopes blown up by the wind. As the horses jogged out into the arid wastes, clumps of bright blossomed cacti and occasional buttes of rock rising sharply out of the desert arrested the attention of the boys.

“Do people actually live out here?” Frank inquired of Señor Marcheta.

“It is not all desert, of course,” replied his host. “There are the oases, and sometimes large lakes, where wandering bands of Indians stop.” He glanced at his compass. “This oasis to which we are going is a fertile place. Up in Chihuahua this desert was known as the Llano de los Cristianos, because in the early days of the Jesuit padres many converts were driven out of the mountains by those who refused to be converted. They were literally forced into the desert, and wandered from place to place.”

“Wouldn’t they die of thirst?” asked Joe.

Juan laughed.

“There is plenty of water on the desert,” he said.

Joe stared at him unbelievingly.

“Cactus,” explained Juan. “Every species of cactus has its water reservoir. Some have them below the ground, others above. The barrel cactus has saved hundreds of desert travelers from dying of thirst.”

As the sun rose higher in the clear sky the heat became more intense. Frank and Joe were not able to keep up with their more experienced companions, and bit by bit lagged behind.

“It’s all a grand experience, Frank,” said Joe. “I wouldn’t have missed it for anything. Just the same, I don’t believe we’re going to find any trace of Pedro Vincenzo.”

“We’ll have something to tell the folks back home at any rate. Boy! It’s warmer out here than I bargained for. I’m getting thirsty.”

“Don’t let that worry you,” Joe replied, swinging himself out of the saddle. “There’s a fine big cactus just a few yards away. I’m glad Juan told us about them.”

He strode over to the large spiked plant that rose from the sands and took a tiny folding cup from his pocket. He broke open the cactus with his knife and dipped into the nectar.

“Come and try it,” he invited, draining the contents of the cup.

“What does it taste like?”

Joe made a grimace.

“Sort of bitter and sort of sweet,” he said. “It isn’t bad, though.”

Frank climbed out of the saddle.

“The desert beats the city all hollow,” he remarked. “You don’t find drinking fountains every five yards apart in town.”

Joe handed his brother the cup and motioned toward the cactus plant.

“Help yourself to a nice clear drink.”

Frank was just dipping into it when they heard a thunder of hoofs. The boys looked up to see Juan riding swiftly toward them. He was shouting and gesticulating wildly.

“I wonder what’s the matter!” exclaimed Frank, the cup raised halfway to his lips.

In another moment Juan rode up in a cloud of sand, flung himself out of the saddle, and ran toward them.

“Don’t drink it! Don’t drink it!” he cried, and dashed the cup out of Frank’s hand.

“Why?” demanded Frank.

“I forgot to tell you. Some varieties of cactus contain deadly poison.” Juan looked at the plant. “And this is one of them!” he declared.

Joe uttered a gasp of horror.

“I just drank some!” he gasped.

The Hardy boys were white with terror. Juan wrung his hands.

“It’s all my fault,” he cried. “I should have warned you. How much did you drink?” he demanded.

“A cupful.”

Señor Marcheta was riding toward them and Juan summoned him to hurry.

“We’ll have to get you back to the town right away,” the Mexican boy snapped. “Perhaps, if we get there in time, we may be able to find medicine to counteract the poison.”

“I’m beginning to feel sick already,” said Joe dolefully.

Señor Marcheta’s horse thundered up to the boys.

“What’s the matter?” demanded Juan’s father in alarm.

Then, when he saw the broken cactus plant, his face became serious, and he swung himself out of the saddle.

“He drank from a poison cactus,” said Juan.

Señor Marcheta strode quickly over to the plant and examined it. Finally he turned aside with a sigh of relief.

“That was a narrow escape,” he said to the Hardy boys. “This species is very like a poison cactus, but fortunately it isn’t. Another variety——”

“And harmless?” asked Joe.

“Quite harmless,” he replied, greatly to their comfort. “After this, do not drink from a cactus unless you ask me about it first. Some of them contain poison, while others hold a drug that would put you to sleep in a few minutes. It’s very fortunate that you happened to drink from a harmless one.”

Juan mopped the sweat from his brow. He had been trembling with fear.

“That gave me a bad scare,” he admitted.

“How about me?” asked Joe with a grin. “I thought I was going to drop dead on the spot.”

“A miss is as good as a mile,” said Frank, climbing back on his horse. “Let’s get going. That was a lesson we’ll remember for a while.”

The four resumed their journey across the great desert, interested in the bright-hued lizards that lay sunning themselves lazily in the sand. Occasionally a great horned toad would hop across their path.

They finally came to a butte of reddish rock, deeply seamed and worn away by the impact of sand blown against it in the course of years. As they were riding around it Señor Marcheta’s horse suddenly lurched, then stumbled and fell. The Mexican was a good horseman, and managed to slip one foot out of the stirrup and leap to the ground just as the animal went sprawling. The horse had stepped into a hole that had been hidden from view by a hillock of sand. When the rest of the party dismounted and went over to the steed, they saw that its leg was oddly twisted.

“Broken,” said Señor Marcheta, after several vain attempts to help the horse to its feet.

Juan whistled ruefully.

“I guess that puts an end to the trip,” he said.

Señor Marcheta did not answer. He was examining the animal’s leg. After a while he stood up and drew a revolver from his belt. He patted the horse’s head gently.

“Good-bye, old fellow,” he said. “I can’t leave you to die of thirst in the desert.” Then, turning about, he said to the boys, “Look the other way!”

After they had done so a shot rang out. When the boys looked around again the horse was lying motionless in the sand.

“We cannot go ahead, that is certain,” said Juan. “You’ll have to ride with me, Father.”

“It is too bad, especially when we have come so far,” said Señor Marcheta reluctantly. Then he shaded his eyes with his hand and gazed out across the desert. “Someone is coming,” he remarked.

Frank and Joe could see no one. They could distinguish nothing but rolling sand dunes extending like great waves far into the distance. However, a moment later a figure began to rise above the crest of one of the dunes. First they saw his head, then his shoulders, then the head of a horse. Finally animal and rider came over the top of the dune. The man reined in his steed, stood up in the stirrups, and gazed at the travelers.

He was a magnificent figure in the sunlight; a tall, broad-shouldered Indian with coppery skin, riding a wiry little pony. A moment later, satisfied that Señor Marcheta’s party were friendly, he dug his heels into the pony’s flanks and rode toward them.

“A full-blooded Yaqui Indian,” explained Juan as the stranger approached. “Perhaps he’ll be able to help us.”

The Yaqui raised his arm in greeting as he came up. Señor Marcheta uttered a cry of recognition.

“Why, I know this man!” he exclaimed. “He once worked for me.”

It was evident that the Yaqui also recognized Señor Marcheta. They exchanged a few friendly words in Spanish. Frank and Joe were greatly interested in the newcomer. They had never seen a finer specimen of manhood. He was powerfully built, lean and athletic, with the clear eyes and untroubled face of one who lives close to nature.

Señor Marcheta and the Indian talked for some time. Finally Juan’s father turned to the boys.

“The Yaqui has offered to take one of us back to town with him for another pony. It will be too heavy a load for his horse if I ride with him.”

“I’ll go,” said Frank readily.

“Are you sure you won’t mind?”

“Not a bit of it. But do you think I could find my way back again?”

“The Yaqui will come back with you. He couldn’t get lost in the desert if he tried. He has promised to guide us when he returns. In fact, he tells me that the oasis known as the ‘Headquarters’ isn’t very far from here.”

The Indian rose in his stirrups and extended his arm toward the northeast, where a distant line of dunes stretched out before them.

“Over there,” he said. “Not far. When the sun sets you will be close.”

Arrangements were quickly made for the exchange of horses. Señor Marcheta took Frank’s pony while the elder Hardy boy climbed up into the saddle behind the Yaqui. A few moments later the two parties separated, Frank and the Indian toward the town, Joe and the Marchetas heading on into the desert.

The sun was just sinking toward the western horizon in a blaze of glowing light, when Juan suddenly reined in his pony.

“We must be careful now,” he said. “I think I see a camp against the sky. Yes—there are trees—and tents.”

“Your young eyes are better than mine,” said Señor Marcheta, coming to a stop. “I can see nothing.”

They had halted at the top of a low butte. Great sunbaked leagues of desert stretched illimitably before them. Joe followed the direction of Juan’s gaze, and in the distance could barely distinguish a few trees silhouetted against the sky.

“It is the oasis,” said Juan. “I think we had better stay here until it becomes dark.”

They dismounted, and ate a hearty meal from the provisions they had taken with them from the inn. Beneath the rim of the butte they knew they were secure from observation by anyone in the distant camp. The sky flamed with glorious colors as the sun slowly sank beyond the horizon. Darkness came swiftly, bringing a welcome coolness after the heat of the day.

“We shall ride on now,” decided Señor Marcheta finally.

The sky blazed with stars. The pink glow of a campfire indicated the location of the oasis as the party rode ahead. Fortunately the successive sand dunes afforded plenty of cover so that they were able to approach within half a mile of the place without fear of being observed. Then, in a little hollow out of sight of the camp, they hobbled their horses.

“Let’s creep up closer,” suggested Juan. “Maybe we can learn who is camping there.”

Señor Marcheta was dubious.

“We may learn nothing, and if we are seen we may get a bullet or two for our curiosity,” he said.

“Perhaps Pedro is here. We can’t give up now, after having come so far.”

Señor Marcheta was fully alive to the dangers of stealing up to spy on a desert camp in the dead of night, but Juan and Joe finally persuaded him to do so.

“For a little while, then,” he agreed. “But you must not go too close. They have sharp ears, these people of the desert.”

The three made their way to the top of the dune. Now they could see the campfire clearly. The light shone on a scattered group of tents and on the calm waters of the oasis, in which the clear stars were reflected as if in a mirror. Figures moved to and fro in the ruddy firelight. Soft music came from a guitar.

Bit by bit Joe and his companions crept over the crest and moved silently down the slope in the direction of the oasis. The Hardy boy’s heart was pounding with excitement. The three made scarcely a sound in the soft, yielding sand as they crept closer to the camp. The night was very still. The music of the guitar thrummed dreamily. They heard a burst of laughter, and a man approached the fire. He threw on fresh fuel so that the flames leaped higher.

“I wonder if Pedro is really here?” said Joe in low tones.

“Perhaps we shall soon know,” Juan replied.

There was a warning whisper from Señor Marcheta.

“Silence!”

When Señor Marcheta and the two boys were close enough to the camp to distinguish what was going on, they lay perfectly still in the sand. They were at a safe distance beyond the radiance of the fire and well in the shadows of a sand dune that would afford protection of a kind, should they be forced to beat a hasty retreat.

The firelight shone upon about a dozen men and women who appeared to be gypsies. They were clad in quaint, colorful costumes, and two of the girls were dancing to the soft music of the guitar. After a while a man lying near one of the tents began to sing. It was evident that the party had no suspicion that they were being watched.

Suddenly Joe gripped Juan’s arm.

“Look!” he whispered. “On the flap of the largest tent. Do you see it?”

Juan followed the direction of Joe’s pointing finger.

“I see a mark,” he whispered in reply. “The fire is burning too low to give enough light for me to make it out clearly. Ah, the flames are rising again. I can see better now. Why, it is the same—the same mark——”

“That was on the door of your home,” returned Joe excitedly.

They could see it distinctly now in the light cast by the flickering flames. It was the familiar symbol of the letter P in a blaze of fagots, the same strange symbol the Hardy boys had found on the door of Pedro Vincenzo’s room in Bayport. Juan and Joe were puzzled over this odd coincidence, with the latter positive now that Pedro Vincenzo must have some connection with the camp.

The music died away, the dancing girls crouched down beside the fire, and a man stepped out of the shadows. He was tall and dark-skinned, with coal black hair, and wore a serape flung carelessly about his shoulders.

He began to speak to the others in Spanish, which Joe could not understand. Juan, however, listened intently and after a while translated the speaker’s remarks.

“He is complaining,” whispered Juan. “He says they have not been paid for a long time. Their supplies are running low. He wants to know if the others are content to wait here much longer.”

There was a low murmur of dissent from the men around the fire. The speaker paced up and down, gesticulating, talking in a loud, harsh voice.

Juan gave a start of surprise.

“Pedro!” he whispered. “He mentions the name Pedro.”

He listened for a while, then continued.

“If Pedro does not come soon they will have to go out and steal.”

One of the listeners spoke up in a quiet, authoritative voice. Juan translated:

“This man says that they must not steal. They are fools, he tells them, to wait for Pedro. He believes something has happened to Pedro, that he is either dead or in jail, and that he will never return.”

The man in the serape—the one who seemed obviously to be the leader of the band—then spoke again.

“He is suggesting that they break camp and go home. It is only a day’s ride west of the oasis.”

The leader’s talk seemed to make a distinct impression upon his followers. One man after another got up and spoke. Juan had some difficulty keeping up with them, but the sum and substance of it all appeared to be that they thought they had waited long enough, and that they would risk starvation in the desert should they remain.

“Pedro is not with them, that is certain,” whispered Señor Marcheta. “I believe these are Pedro Pancho’s followers, beyond a doubt. We have come on a wild-goose chase.”

The leader then raised his hand for silence. He spoke only a few words, but what he said was evidently important. No one answered him and all his followers looked uneasily at one another.

“I cannot understand this,” Juan whispered. “He asks them what they are to do with the American prisoner.”

“Prisoner!” Joe almost shouted aloud. To him the words ‘American prisoner’ could mean only one man and that man was Elmer Tremmer, the missing witness.

Juan glanced curiously at Joe. He could not understand the reason for the other lad’s excitement. He listened as the leader of the gang went on speaking.

“He is saying,” Juan whispered finally, “that Pedro may never come for the prisoner if they take the American into the mountains with them. He is suggesting that they leave the man in the desert.”

Evidently this idea was not favored by the others. Two or three of the men grunted objections. One of them, according to Juan, said that they must keep the prisoner if they ever hoped to get money from Pedro.

“Pedro may come. If we do not have the prisoner he will never pay us. But if we have the prisoner we can force Pedro to give us our money,” the fellow argued.

Joe was greatly agitated. He craned his neck as he tried to get a better view of the camp, and attempted to see the faces of the people around the fire.

“I want to know more about that American,” he whispered to Juan. “I wonder where they keep him. I’m going closer.”

“Don’t be foolish,” the Mexican boy urged. “You may be caught.”

“I’ll be careful.”

Although Juan and Señor Marcheta begged him to remain where he was, Joe began to crawl away through the sand. He wanted to work around to the rear of the camp in the hope that he might learn where the prisoner was being kept. In a few moments the darkness swallowed him up. Juan and his father were left alone on the slope.

Joe kept well out of range of the firelight. He crept slowly around toward the back of the tents, but this spot was quite deserted. Was the prisoner in one of the tents?

He was positive that the man must be Elmer Tremmer and that Pedro had left him there in charge of this roving band of natives. In any case, if the prisoner was an American he must be rescued. Perhaps when Frank and the Yaqui returned they might be able to think up a plan.

Some distance over toward the big pool of water that shone in the starlight Joe caught sight of a figure lying in the sand. Another form was crouching nearby, the figure of a native with a blanket flung over his shoulders and a rifle across his knees.

Joe went as close as he dared. He could hear the sounds of talk and laughter from the direction of the campfire. The rifle bearer stirred uneasily and looked about him. Joe lay motionless. The man shifted the blanket a little and settled down again. The figure in the sand did not move.

Inch by inch Joe crept nearer. He was sure that the man with the rifle was a guard and that the other was the American prisoner. The boy edged around so that he was behind the crouching form.

The figure lying in the sand moved an arm, groaned, then sat up. He yawned and stretched.

“Are you people trying to starve me?” he muttered. “I’m hungry.”

The guard growled something unintelligible.

“I wish somebody around here could talk English,” said the prisoner bitterly.

He turned at that moment and the light of the fire shone dimly upon his face. Joe could not see the man very clearly, so he edged forward a little more, trying to get into a position where he could catch a glimpse of the prisoner’s features.

“I don’t see why you have to watch me all the time,” grumbled the American. “Don’t worry. I won’t run away.”

The native did not answer.

Just then the prisoner turned slightly and the light fell clearly upon his face. Joe leaned forward, staring.

Had he found Elmer Tremmer, the missing witness, at last?

Joe Hardy knew Elmer Tremmer by sight. He had seen the man in Bayport several times and remembered him as a quiet, inoffensive little fellow, a rather gray, inconsequential man of about fifty. Elmer Tremmer, as Joe remembered him, had a gray mustache and wore horn-rimmed glasses.

Now, as the light fell upon the face of the prisoner in the desert, Joe suppressed a murmur of disappointment. This man wore no glasses. Neither had he a mustache, but this was not surprising, as the barber in the Texas town had intimated that Elmer Tremmer had had his mustache removed. The prisoner’s face was unshaven and there was a stubble of half-grown beard about his chin. In the dim light Joe was unable to identify him.

A moment later the man turned his head away. Joe wished heartily that he had known the missing witness better when he was in Bayport. Then he might have identified the man by his voice.

Suddenly, from over in front of the tents, he heard a shout of alarm. Yells of excitement broke out. A man came running out of the firelight and called to the prisoner’s guard. In a moment the sentinel leaped to his feet and urged the American before him into one of the tents. Joe could see men running back and forth.

“They’ve caught Juan and Señor Marcheta!” he thought.

Quickly he scrambled to his feet and ran back into the darkness of the sand dunes. Over to one side he caught a glimpse of dark figures hurrying out of the camp toward the slope on which Juan and Señor Marcheta had been lying.

Joe knew that he would only be courting disaster if he went toward his comrades now. It would be sheer foolhardiness should he try to rejoin them. He made a wide circle out across the desert, taking shelter in the hollows of the dunes, until at last he was out of sight of the camp altogether. Once he heard the report of a rifle and an outburst of shouting.

What had happened? There was no doubt in his mind but that his friends had somehow been discovered. If they had been taken prisoners, his own plight was serious.

He got to his feet and walked down a long hollow between the sand dunes. No longer could he hear sounds from the camp. The stars flamed overhead and the silence was so deep that he might have been the only living being within hundreds of miles.

He crept quietly up to the top of the next dune. Suddenly he stopped, his heart in his mouth, for the silence was broken by the low murmur of voices.

Joe flung himself flat in the sand and lay there. Against the sky beyond the top of the dune he saw a moving figure. Joe almost cried aloud in relief. Señor Marcheta and Juan were up there on the other side of the dune. Joe Hardy climbed over the crest.

“Juan! Señor!” he whispered.

They wheeled about.

“Joe!” cried Juan eagerly. “Is it you? We’ve been so anxious!”

“And I’ve been worried about you,” Joe said as he came up to them. “I was over on the other side of the camp when I heard the row and I was sure you’d been caught.”

“They didn’t see us,” Juan said. “Somebody in the camp heard us talking and raised the alarm. They all came out to look for us, but we were mighty well hidden by that time. So they decided they had been mistaken and gave up the search.”

“I think we had better clear out of here anyway,” Joe suggested. “There is nothing we can do and we may bring trouble on ourselves if we hang around.”

“We will go back to the place where we left the horses,” Señor Marcheta said.

Joe told them nothing about the American prisoner. He went back down the slope with them and soon they were retreating from the vicinity of the camp. When they returned to the place where they had hobbled the ponies they wrapped themselves up in their blankets and went to sleep.

Dawn broke over the desert in a blaze of glory. Frank and the Yaqui had promised to meet Joe and the Marchetas at an odd-shaped butte with a top like a pyramid. Juan said that the Indian was sure to keep his word.

“He’ll be there, and exactly when he promised,” said the Mexican boy. “The Yaquis are very dependable.”

“This man in particular,” declared Señor Marcheta. “When he worked for me I trusted him above all my other employees.”

They set out once more under the blazing sun. Soon the distant oasis was lost to sight beyond the rolling dunes of sand. At about mid-morning Juan spied a tiny object in the distance.

“Here they are!” he said confidently.

He was right. Before noon Frank and the Yaqui were riding up to them. Joe could not help but marvel that the Indian had found his way back to the appointed place so unerringly across the trackless desert.

Frank, mounted on a small dappled pony that the Yaqui had borrowed in town, drew up beside his brother.

“Looks as if the rest of the trip is off,” he said quietly.

“What do you mean?” asked Joe.

He noticed that the Indian was talking in an earnest voice to Señor Marcheta and Juan.

“There was a message waiting for Juan’s father when we got back to the town,” Frank said. “Apparently they’re needed back home at once.”

“Anything wrong?”

“No. It’s a business matter.”

“But we can’t turn back now!” exclaimed Joe. “It’s impossible. Why, Frank, I’ve stumbled on the biggest clue of all. There’s an American prisoner in that camp at the oasis. For all I know, the man may be Elmer Tremmer.”

Frank was greatly excited by this news.

“An American prisoner!” he exclaimed. “How do you know?”

“We crept up close to the camp last night and overheard the people talking about him. They’re Pedro Vincenzo’s men, I’m sure. Pedro has deserted them and they’re planning to clear out. I saw the prisoner myself—just got a glimpse of him—and I don’t know whether he is Tremmer or not. He didn’t have a mustache and he didn’t wear glasses.”

“We certainly can’t give up the search now,” Frank said decisively. “Even if Juan and Señor Marcheta have to return there’s nothing to prevent us from carrying on.”

“But how could we ever find our way back? We don’t know anything about the desert.”

“The Yaqui does. If we can persuade him to stay with us we won’t have anything to worry about.”

At this moment Juan and Señor Marcheta rode up to them.

“Boys,” said the latter, “I regret extremely that business calls my son and me back to the city. It is a very important matter. The Yaqui brings me a message demanding that we return at once.”

“We were just discussing that,” said Frank. “Would it not be possible for us to stay?”

“In the desert? Alone? I could not permit that. I am responsible for your safety.”

“But if the Yaqui remained with us we would be quite safe.”

“That is true,” admitted Señor Marcheta. “But is it necessary for you to stay? Is this affair so very important?”

“It’s very important,” said Frank. “I can’t explain the whole business to you, Señor Marcheta, but we are trying to help our father in a case. Joe tells me there is an American prisoner in that camp at the oasis. We must rescue him somehow.”

Señor Marcheta nodded.

“But I am afraid three of you will not be able to set the man free. I shall suggest this. When Juan and I get to the town on the edge of the desert, we will send soldiers out to help you rescue this prisoner.”

“That’s a dandy idea!” exclaimed Joe enthusiastically. “We won’t have long to wait, will we?”

“Juan and I should reach the place before evening. We’ll try to send the soldiers out at once. But first of all I’ll ask the Yaqui if he cares to stay.”

Señor Marcheta spoke to the Indian, and it was soon evident that the native was agreeable to remaining with the Hardy boys. Frank and the Yaqui had brought an extra supply of food with them, so that there were no serious obstacles in the way of their remaining. Señor Marcheta, who evidently placed great confidence in the Yaqui, solemnly instructed the man that he would be responsible for the safety of los Americanos. The Indian placed his hand above his heart.

“They will be safe, Señor,” he promised.

In a few minutes the party broke up. Juan and his father said good-bye to their young friends. The Mexican lad was greatly put out because his share of the adventure had come to such an untimely end. He suspected that there was more excitement to come, but he tried to be cheerful about it and waved gaily to the Hardy boys as he rode away. In a little while the two ponies were hardly more than tiny moving dots on the sunbaked surface of the desert.

“What shall we call you?” Frank asked their coppery-skinned guide.

“Yaqui,” returned the native promptly.

“Yaqui it is, then. Señor Marcheta has told you what we want to do?”

The Indian nodded.

“We are to stay until the soldiers come.”

It was a long wait, and a monotonous one. Frank and Joe managed to snatch a little sleep in the shade of a great cactus plant, and whiled away the afternoon until night fell. Frank was eager to push on toward the oasis and spy out the ground for himself, but Yaqui did not favor the idea.

“We are three,” he pointed out. “They are many. If we are seen, it may be too late when the soldiers come.”

“That’s reasonable enough,” agreed Joe. “It wouldn’t pay to spoil it all by being impatient. I suppose we had better wait.”

Under the desert stars they spent the night. When morning came the boys eagerly scanned the horizon for some sign of the promised soldiers. But the skyline was unbroken. There was nothing but a great expanse of sand, shimmering in the heat. The sun rose higher and still there was no moving object among the distant dunes.

“Perhaps there weren’t any soldiers in the town,” said Joe, disappointed.

“Perhaps they wouldn’t come.”

Yaqui said nothing. He crouched on the sand, his arms around his knees, and gazed steadily into the distance.

Toward mid-day they caught sight of a traveler on horseback, followed by a small burro, about a mile to the northeast. He was coming toward them from the direction of the oasis.

“Perhaps this is one of Pedro’s men!” exclaimed Frank.

As the rider approached they saw that he was a Mexican. He hailed them in his own language, evidently surprised to see the three camped in such a place. Yaqui called back to him, and when the traveler rode up, asked him questions. He was evidently inquiring about the people at the oasis, as the boys judged by his frequent gestures in its direction. There was a lengthy conversation between the pair and at last Yaqui turned to the Hardy boys.

“This man has just come from the oasis.”

“And what does he say?”

“There is no one staying there now. But he saw a caravan moving toward the edge of the desert.”

“They’ve given us the slip!” cried Frank. “They’ve broken camp and gone back to the mountains after all.”

“We’ll never find them now!” said Joe disconsolately.

Yaqui and the stranger exchanged a few more words. Then the Mexican rode away, the burro bells tinkling solemnly as he resumed his lonely journey across the sand wastes.

“Can’t we set out after them, Yaqui?” asked Frank desperately. “We must free that prisoner.”

“If only the soldiers would come,” Joe groaned.

Yaqui stood up, shaded his eyes, and gazed out across the desert for several minutes. Finally he shook his head.

“No soldiers yet,” he murmured. Then, turning to the boys, he said, “These people are far ahead. It will be easy to follow their trail across the desert, but we may lose them when we reach the hills. Yet we can try.”

“Let’s do so by all means,” declared Frank, “It’s our only chance. The soldiers may not get here until tomorrow.”

“Tomorrow will be too late,” said Yaqui. “If we are to follow the trail we must set out at once.”

It was aggravating to think that the solution of the mystery had been snatched out of their grasp in the very moment of success. The Hardy boys were convinced that the presence of the American prisoner in the desert camp was the answer to the riddle of Tremmer’s disappearance.

“Soldiers or no soldiers,” Frank said, his jaw set with determination, “we’re going to follow those oasis people!”

Their preparations completed, the boys mounted their ponies. Yaqui swung himself lightly into his saddle and the group started out toward the fertile spot where the natives had been camping. The Indian set the pace.

It was not yet sunset when they reached the oasis. The waters of the pool looked cool and inviting in the shade, a welcome in direct contrast to the harsh bleakness of the desert surrounding it.

The camp was, of course, deserted. Yaqui dismounted and examined the tracks in the sand made by those who had left.

“Their burros are heavily loaded,” he said at last. “They will travel slowly. Perhaps we may be able to overtake them before they reach the edge of the desert.”

The boys were hot and tired after their ride, and seized the opportunity to bathe in the waters of the lagoon, and to take a much-needed rest in the cool shade.

As Joe stretched himself at full length, his toe suddenly touched an odd-shaped stone. The boy peered down at the mineral.

“What’s the matter?” queried Frank. “Thought you were going to sleep.”

“That rock never belonged here,” muttered his brother. “It was brought to this spot by some one.”

The Hardys, scenting a mystery, at once forgot their fatigue. They lifted the peculiarly marked stone and set it to one side.

“Now, I wish I were a ground hog,” laughed Joe. “I’d like to do a little digging.”

“What do you think you would find?”

“I confess I don’t know what to expect. But I really believe this is a marked spot. Let’s do a little excavating.”

Frank agreed. Furiously the boys drew aside great heaps of earth. Suddenly Joe’s hand touched an object.

“I’ve found something,” he exclaimed excitedly.

“Sure as shooting,” agreed Frank. “It’s a piece of antelope skin,” he continued as he leaned closer over the hole.

“It’s a cover to something.”

“Look!” cried Frank as he cleared away more soil.

Joe bent nearer the hide. Clearly burned into the fur was the unmistakable symbol P with the burning fagots beneath.

“Do you suppose—” asked Joe with awe, “that we have uncovered——”

The young detective got no further in his supposition, for at that moment Yaqui, who had been asleep a little distance away, aroused himself. When he saw the stone and the digging, he cried out in alarm:

“Stop! Stop! You must quickly cover the dead man! Evil spirits—you will be——”

The Indian did not finish, so amazed was he at the change in the attitude of the two boys. They were hastily throwing back the dirt. To the untutored mind the native was at once convinced the lads were fearful of the dreaded punishment his gods would mete out to the grave despoilers. It was an ill omen—no doubt the search for the fleeing campers would come to some bad end.

However, Joe and Frank were whispering between themselves about an entirely different angle of the case.

“Gee! I didn’t expect this, Frank.”

“Neither did I. Wouldn’t Chet find an excuse to run off if he saw this!”

“But that marking on the skin was plain. Do you suppose the fellow died a natural death, or was killed for disobedience?”

“I believe that brand is the signet of a cruel, heartless man whom we must track down,” answered the older Hardy brother.

The stone was replaced on the exact spot from which the lads had taken it. Then Yaqui brought the ponies together.

“Frank,” whispered Joe a bit hoarsely, “you don’t believe that poor fellow buried there could be Elmer Tremmer, do you?”

“I was wondering that myself. Perhaps we should have investigated further.”

“Well, it’s too late now. We’ll just have to trust to luck that the missing witness is ahead of us in company with the natives.”

The group resolved to push on without delay. As darkness fell several hours later, they were obliged to slacken their pace. Yaqui was finding it more difficult now to follow the tracks. Then, too, their ponies were tiring. To add to their difficulties a light wind sprang up, blowing stinging clouds of sand into their faces.

“That is bad,” said Yaqui. “It is blotting out the trail. We will make camp for the night.”

Anxiously the boys gazed into the darkness, hoping that they might see the glow of the fugitives’ fire.

“No such luck,” muttered Frank. “And worse than that, if this wind keeps up there won’t be a track left for us to follow.”

In the morning the situation looked hopeless to the unpracticed eyes of the Hardy boys, but the three set out again. This time they made slower progress, for Yaqui was scanning the sand intently. Here and there, especially in the lee of the buttes, he found indentations that convinced him he was on the right course.

At length the trio came to the desert’s edge. The wastes gave way to rock, then to fertile country; but it was almost as lonely. The work of trailing the fugitives became more and more difficult. They came upon a half-breed squatter who told them he had seen the caravan passing to the westward. It was a long time before Yaqui picked up the track again. There were no towns, no villages where information might be obtained. Their progress became slower than ever.

On the second day the Hardy boys were almost ready to give up.

“Do you think we’ll ever find them, Yaqui?” asked Frank.

The Indian shrugged.

“Maybe,” he answered. “Not very far ahead. We lost much time.”

Their food supply had been exhausted for some time, but they managed to buy edibles from the natives they encountered. Frank and Joe would have turned back, but Yaqui pointed out that it would be easier to return to the city by going across country than by making the long return journey through the desert again.

“It’s hopeless,” Frank said on the third day, as their weary ponies trudged toward a tiny adobe hut which their guide had spied in the distance. “We’ll tell Yaqui to set his course for home.”

“We’re lucky we have him,” remarked Joe. “I’m sure I haven’t the faintest idea where we are.”

“Somewhere in Mexico, that’s all I know. But he’ll get us back to the city safe enough. I hope Dad isn’t worrying about us.”

As they drew nearer to the hut they could see that the place was completely surrounded by a fence of tangled and prickly cacti, so formidable, that anyone attempting to squeeze his way through the hedge would have his clothes torn off his back.

“A robber would think twice before he’d try to climb over that,” remarked Frank.

“It is nopal cactus,” explained Yaqui. “It is not only a fence but a garden. The tuna fruit grows on it.”

“How do we get in?”

Yaqui smiled. A native was slouching out of the hut. The man came across the little yard and called out to the Indian, who answered him. The man, a half-breed, bowed respectfully to the boys’ guide, then hastened to open a gate in the hedge. A few mongrel dogs yapped as the travelers rode into the yard, but their owner sent them yelping back behind the hut.

Two other men lounged out of the doorway into the sunlight. They looked on in silence as the boys dismounted. Frank and Joe were conscious of their suspicious and uneasy glances.

“We don’t seem to be very welcome,” Joe said.

Yaqui shrugged.

“Bah! Half-breeds!” he said contemptuously. “I am a pure blood Yaqui. They shall do as I say.”

It was evident that the shabby natives recognized Yaqui’s superiority. The very tone of his voice was commanding as he ordered food. He had a long talk with the men in their own language, presumably asking if they had seen the caravan. But they shook their heads.

“There is something strange here,” Yaqui muttered. “These fellows are lying.” Although he persisted in his questioning, he failed to elicit any information.

The travelers went into the hut, where dishes of native food were placed before them. The Hardys were almost sickened by the queer preparations which seemed, as Joe said, to be made of “red pepper and lye.” Yet they were so hungry that they forced themselves to make a meal.

While the boys were eating they heard a thunder of hoofs beyond the fence. One of the half-breeds ran out to open the gate. A native rode into the yard and dismounted. The two men talked together in low tones and finally walked toward the hut.

The newcomer was a lean, swarthy fellow with a drooping mustache. He darted a sharp glance toward Yaqui and the Hardy boys as he crossed the threshold. Suddenly Frank rose halfway to his feet, stifling an exclamation of surprise.

“What’s the matter?” asked Joe.

His brother sat down again. The half-breeds were looking at him suspiciously.

“Nothing,” he said.

A moment later, when the men in the hut were talking quietly in a corner, he gripped his brother’s arm.

“Joe,” he whispered. “That man looks like the fellow who attacked me in the garden at Señor Marcheta’s place.”

“The fellow who knocked you out?” gasped Joe. “Are you sure?”

“I’m almost positive,” replied Frank excitedly. “I had no more than a glimpse of the man at the time, but I’m certain he’s the same one.”

The native glanced toward them at this moment, whereupon Frank tried to feign indifference. He was convinced that the man was in Pedro Vincenzo’s hire, yet he knew that any attempt to confront him with the fact would be useless.

The stranger came over to Yaqui and began to talk to him. The Hardy boys could not understand the conversation, but they assumed that the newcomer was asking their guide questions about them. They heard the Indian mention the name of Señor Marcheta, then “Americanos” and “Hardy.” Finally the man withdrew, said good-bye to the half-breeds, and strode out into the yard. A moment later he rode away.

“What did he ask you, Yaqui?” inquired Frank.

“He wanted to know where you came from and why you were here.”

“You didn’t tell him, I hope.”

“I told him nothing.”

“You mentioned our names.”

“Yes. But there was no harm in that.”

The Indian then told them he had learned from the half-breeds that there was a road about a mile from the hut. By traveling up into the foothills they would be able to make connections with a highway which would take them to the city.

“These men know nothing of the caravan. I think we should waste no more time,” Yaqui said. “However, it is as you wish.”

“Yes, I guess we had better go back to town,” Joe agreed.

They were disappointed, for the boys had convinced themselves that the American prisoner whom Joe had seen in the camp at the oasis had indeed been Elmer Tremmer. To have lost the trail by such a narrow margin was inexpressibly aggravating.

“No use crying over spilled milk,” Frank said philosophically. “We’ve lost out, so we may as well go back to town and tell Dad what happened. Perhaps he’ll be able to find some trace of that caravan.”

They paid the half-breed for the food they had eaten, then went out into the yard. Suspicious eyes followed them as they mounted their ponies and set out again, Yaqui leading the way. They found the road without any trouble. It was little more than a dusty cow-path running into the foothills.

Frank could not free his mind of the recollection of the native who had come to the hut.

“What was one of Pedro Vincenzo’s men doing in such an out of the way place?” he asked, as he and Joe jogged quietly along under the burning sun. “If that wasn’t the fellow who knocked me out that night I tackled Vincenzo, I’ll eat my hat.”

“Perhaps he was with the caravan,” suggested Joe. “He might have come back to see if they were being followed.”

“Perhaps,” Frank agreed doubtfully. “I’m sorry Yaqui let him know our names. It was an accident, of course, but it’s unfortunate it had to happen. Somehow, I have a feeling that we haven’t seen the last of that Mexican.”

Before them the road wound through the hills. Far in the distance they could see the grim mass of the mountains against the sky. When they looked back they could see the enormous desolation of the desert. Now that the excitement of the chase had worn off they felt tired and dispirited.

The road wound about the foot of a steep hill, twisting and curving so that often they could not see the path for more than a few yards ahead. Yaqui was riding around one of these bends when his pony suddenly shied violently, almost throwing its rider from the saddle.

The same instant the boys heard a shot and a chorus of wild yells. They saw two Mexicans rush out from a place of concealment among the bushes at the roadside and grab the Indian’s horse by the bridle. Frank looked back. A pony and rider came plunging down the slope in a cloud of dust and stones, cutting off escape to the rear.

It all happened so suddenly that neither Frank nor Joe could grasp the situation, for the roadway appeared to be alive with swarthy, evil-faced men, some on horseback, others on foot. They seemed to have sprung up out of the ground. One burly ruffian seized the bridle of Joe’s pony, which was rearing and plunging in fright, while another snatched the reins out of Frank’s hands.

“Bandits!” cried Joe. “We’re caught!”

There were about a dozen of them, and it was plain that they had been lying in ambush at the bend in the road. The men were heavily armed and as unsavory a crew of rascals as can be imagined.

One fellow, who was mounted on a spirited pinto pony, seemed to be the leader, for he stood up in the stirrups and shouted orders at the others. He was a stout, villainous looking fellow with a livid scar down his right cheek.

Yaqui made no resistance, but raised his arms in the air. The attack had been so sudden and so well planned that the bandits were in command of the situation from the start. Frank and Joe followed their guide’s example and put up their hands also.

“Thank goodness, we haven’t much money with us,” said Frank. “I suppose that’s what these men want.”

“Unless they intend to hold us for ransom,” muttered Joe.

The bandit leader rode toward the boys, showing his teeth in an evil smile. He said something that the Hardys could not understand. Frank pointed to their guide.

“What does he want, Yaqui? Our money?”

With a bandit clinging to the bridle of his horse, Yaqui rode over and spoke to the leader. Then he turned to the boys and shook his head.

“It is not so simple as that,” he said. “You are to give him your money, yes. But more than that, we are to be taken prisoners.”

“Why?” demanded Frank angrily. “Tell him he can have our money if he’ll let us go. We have only a few dollars anyway.”

Yaqui interpreted this to the bandit chief, who merely shook his head curtly and rasped out a sharp command, motioning to the boys’ pockets. Reluctantly the Hardys handed over the money in their possession. The bandit leader stuffed it into his pocket, then wheeled his pony about and shouted to his men.

Instantly there was great confusion. More horses were led out from hiding places among the bushes, and in a few minutes all the outlaws were in the saddle. The Hardy boys and Yaqui were in the middle of the milling group, so that there was no chance of their making a break for liberty.

“Pedro Vincenzo is at the bottom of this,” declared Frank. “I know it.”

“That’s why his man came to the hut. He wanted to know where we were and where we were going,” Joe said disconsolately. “What do you think they intend to do with us?”

Frank was angry now. He spoke to Yaqui.

“Tell them we’re not going with them. Tell their leader that we’re American citizens and that Señor Marcheta will have every soldier in Mexico on their trail if we disappear.”

The Indian obeyed. He interpreted Frank’s words to the bandit leader. His only answer was a scowl and an ugly laugh.

“So?” gritted the man with the scar. “The Americanos do not weesh to come weeth us?” He rode up beside Frank’s horse. “Señor,” he said, “you are my prisoner. You weel do as I say.”

“I warn you that we’re American citizens,” declared Frank. “We have friends. You won’t get away with this. The soldiers——”

“Bah!” sneered the bandit chief. “Soldiers! The soldiers have try to catch me for years. And always they fail.”

Then a change came over his face. His eyes became narrow and cruel. His hand swept to his belt and rose again. In the sunlight there flashed the blade of a knife!

Involuntarily Frank drew back as the wicked knife was brandished before his eyes. Joe cried out in alarm, for he thought the bandit chief intended some harm to his brother. But the man with the scar only laughed harshly.

“Do you weesh me to use thees knife?” he asked.

Then, thrusting the weapon back into his belt, he swung his horse around and rode back to the head of his men. He struck off down a narrow trail that led away from the side of the road.

Hemmed in by bandits, the prisoners had no choice but to obey. With sinister-faced men on horses ahead and behind them they had no chance to escape, and they knew it. Within a few minutes they were far off the road and following the trail through a wild region that led deeper into the hill country.

“Keep a stiff upper lip, Joe! We’ll see Bayport again—some day.”

Joe mustered up a smile.

“It’s Dad I’m thinking of,” he said. “He won’t know what’s happened to us. And if any search is made for us, it will never be in this part of the country. They’ll hunt for us in the desert.”

“We’ve been in scrapes almost as bad as this one, and got out of them again.”

“That’s true. And who knows—maybe we’ll learn a little more about Pedro Vincenzo. I’m sure he’s back of this business.”

The Hardy boys had obtained very little rest and sleep in the past few days, so eager had they been to press hard on the trail of the caravan. As a result, they were now almost exhausted.

“The only thing that keeps me going,” said Frank wearily, “is the thought that maybe we’re on the trail of Tremmer and Pedro after all.”

Joe glanced at Yaqui.

“What will they do to us?” he asked quietly.

The Indian shrugged.

“Quien sabe?” he replied. “Perhaps we die.”

This was not very reassuring.

“They wouldn’t dare,” cried Joe.

“Who would know?” returned Yaqui. “Who is to say that we came to this part of the country? Who is to say that we did not die of thirst in the desert?”

The boys began to realize that their plight was very serious. It would be almost impossible for Fenton Hardy and Señor Marcheta to trace them, for it was certain that the natives in the huts near the desert would say nothing because of their fear of the bandits.

The trail led toward the hills, and into country that gradually became wilder and steeper. The riders were in the very heart of the mountains, when darkness fell. Great lowering slopes rose on every side. In the distance the boys could hear the roar of a river. In the gloom they could see ahead the mouth of a great gorge.

Up in the high country it grew cold, and the boys were soon shivering. They were weak from exposure and hunger, but they were not allowed a respite.

Suddenly Joe, utterly exhausted, lunged forward and slipped from his horse.

“Joe,” called Frank, “Joe, what is the matter?”

A bandit guard leaped to the ground. His pony, unattended, reared and plunged toward the numb lad on the trail. It was a moment of agony to Frank.

“Let me help my brother,” he shouted.

Suiting action to words, he lashed the offending horse, which side-stepped just in time.

Joe opened his eyes.

“Oh, Frank,” he muttered, “I guess I fell asleep or something.”

But Frank knew better. He realized it was due to lack of food and rest that his brother had been faint, and decided to get better treatment. He set up a terrible howl, and the bandit leader gave a command to the procession.

“Halt!” he roared in Spanish.

“We need something to eat,” shouted the older Hardy boy. “Right now!”

The chief paid no attention to the suffering prisoners; instead, he spoke sharply to one of his men, who dismounted and went ahead on foot. The native’s shadowy figure could be seen entering the gorge. He returned presently and whistled. Then the cortege moved on.

As the group came into the ravine the boys saw lights ahead and the blaze of a camp fire. Two or three natives came running up with cries of welcome.

“Home, sweet home!” said Joe with a wan smile.

This, obviously, was the headquarters of the bandits. The men dismounted and handed their horses over to native servants, then sprawled wearily beside the fire. Stiff and sore, Frank and Joe got down, hungrily sniffing the fragrant odors of food. A brown-faced woman brought them plates of some sort of stew. It was highly seasoned and very hot, but they devoured it gratefully, although at another time they might not have managed to eat it at all.

“Tastes a bit like liquid fire seasoned with brimstone,” said Frank, “but it hits the spot just the same. I’m so hungry I could eat a rubber boot.”

“Without butter,” mumbled Joe, his mouth full.

Finally the bandit chief gave an order to one of his men, who came over to the captives.

“Follow me!”

Along a narrow path he led the prisoners toward the cliff, holding aloft a blazing torch.

“What now?” murmured Frank as they followed their guide.

The trail led up a steep slope, so steep that they had difficulty in keeping a foothold. It went higher and higher until, when they looked back, they could see the light of the bandit camp far below in the gorge. Then they were forced to walk along a narrow ledge on the face of the cliff until the light of the torch revealed the mouth of a small cave.

Here the bandit stood aside, spoke to Yaqui, and motioned the three captives to enter.

“We are to sleep here,” the Indian explained calmly.

The boys were too weary to resist, so they crawled through the small opening. The bandit tossed the torch in after them. Then he set to work sealing up the cave mouth with adobe bricks that were piled about the entrance.

“Surely we’re not going to be tombed up here!” cried Frank.

“This is our prison,” Yaqui said.

Although the entrance was small, the cave itself was of substantial proportions. It contained a few rough pallets of straw, but nothing more. The Indian set the torch in a crevice, and in its flickering light the trio looked gloomily at one another.

“Why, we must be among the cave dwellers!” Joe exclaimed.

“The natives who live here,” explained Yaqui, “are descend from cliff dwellers. Real Indian tribes have nothing to do with them. They are outcast.”

“Why?”

“Because they work with bandits.”

“They wouldn’t help us?”

The Indian shook his head.

“If we managed to get out of here, Yaqui,” said Frank, “do you think you could guide us back?”

“I could find my way,” admitted their guide slowly. “But we will not get away from here. We can only wait.”

“I wonder what these people plan to do with us.”

“Our lives have been spared. It is ransom they want, I think.”

“There’s something more than that. This is Pedro Vincenzo’s work,” declared Joe. “He thought we were getting too close on his heels and he wants us out of the way. That’s my guess.”

“Perhaps,” said Yaqui indifferently.

Why they had been captured did not greatly matter to him. The point was that they were prisoners and that there was very little they could do about it.

“I’d get a great kick out of this, being among the cliff dwellers and all,” remarked Frank, “if I only knew that we could pack up and go home whenever we liked.”

In the guttering light of the torch Joe noticed a strange object on the floor. He picked it up and turned it over in his hands.

“Why, it’s a bracelet!”

The ornament, made of silver, was slightly tarnished. It was set with colored stones. Yaqui examined it with interest.

“Is it valuable?” Joe asked.

“The stones are semi-precious,” said the guide. “It is worth a little money.” He handed back the bracelet with a smile. “A little souvenir to take home with you.”

“If we ever get home,” grumbled Joe.

The bandit who had led them to the cave had finished sealing up the entrance. Now they could hear him clumping off down the narrow trail. Away in the distance the boys could hear the roar of the river and the sound of voices from around the campfire below. It was strange to think that a few short days had brought such a change in their fortunes.

“Just think,” Frank said, “a little more than a week ago we were at home in Bayport. Now we’re in a bandit camp in the mountains of Mexico!”

“That’s what we get for trying to be detectives,” Joe reminded him. “Don’t talk about Bayport. I’m going to sleep.”

“Me too,” Frank answered. “I’m so tired I can’t keep my eyes open.”

The torch was guttering and filling the cave with smoke, so Yaqui extinguished the light. In the darkness there was a rustling of straw and sundry groans and yawns as the prisoners lay down to sleep on the pallets. They were so exhausted that even the worries of their position could not keep them awake. In a very few minutes they had fallen into a deep slumber.

Daylight was filtering into the gloomy cave when Frank opened his eyes next morning. Between the chinks of the bricks at the entrance he could see the bright sunshine. As he stirred and raised himself on one elbow, Joe woke up, blinking.

“Where am I?” the latter muttered in surprise. Then he remembered. “Gosh, I was dreaming I was back home in Bayport and that Aunt Gertrude was yelling at me from the foot of the stairs and telling me I’d be late for school.”

“No school for us today,” Frank answered with a grin. He sat up, stretching his arms. “This isn’t much of a bed, but I surely slept well on it.”

He glanced toward the other side of the cave. Then his jaw dropped and his mouth opened in astonishment.

“Am I seeing things?” he muttered.

Joe sat up quickly. The pallet on the other side of the cave was empty.

“Why—why—where’s Yaqui?” he gasped.

Frank leaped to his feet and circled swiftly around their rocky prison. The Indian had vanished. For a moment he thought their guide might be secreting himself and playing some sort of a joke on them, but he soon saw that there was no hiding place in the cave. The entrance was still sealed up with adobe bricks. Yaqui was gone. Frank sat down, limply on his pallet.

“He has deserted us!”

The Hardy boys looked at each other in dismay. Up to this time the presence of Yaqui had encouraged them, for they knew that if ever they were to escape from the bandits they would have to rely largely upon his help. Now they felt that their only friend had proved unreliable, and had left them to their fate.

“I can’t believe it,” Joe said. “Yaqui isn’t that sort of fellow. He wouldn’t let us down.”

“I don’t want to believe it,” replied Frank. “But how else can you explain it? He isn’t here. He waited until we were asleep and then cleared out.”

“Perhaps he went to see if he could get help.”

“Maybe. But why couldn’t he tell us before he left?”

In the back of their minds was the dread suspicion that Yaqui had left them to the mercies of the bandits, and that the native had sought to save his own life at the expense of theirs. They had trusted him so implicitly that no thought of treachery had entered their minds, so that now the shock was doubly great.

“We’ll have to take care of ourselves,” Frank said, as he went toward the mouth of the cave. “Yaqui must have thought our lives were in danger, or he wouldn’t have deserted us like that.”

“Even now I can’t believe he has let us down. There is some other explanation. I’ll bank on it that he went to get help and just didn’t want to wake us up. That man is honest.”

Frank kicked idly at the bricks across the mouth of the cave.

“I hope we haven’t been left here to starve,” he said. “I could eat three meals all at once right now.”

“What beats me is how Yaqui got out.”

“Since he did, we can.”

The bricks were jammed solidly in the opening. Although Frank labored frantically at them, he could not budge the heavy barrier. Then he noticed that the top of the entrance came to a point, one large brick having been wedged in at that spot to hold the others in place. Joe suggested that this should be the centre of attack.

“It’s the key to the whole blockade,” he said. “Get that one loose and the rest will be easy.”

The top brick itself was not easy to dislodge, however. It was crammed in so tightly and solidly that there seemed to be no chance of its being worked loose. The boys picked up rocks from the floor of the cave and banged and hammered vigorously at the obstacle.

Finally the brick began to yield. Frank and Joe redoubled their efforts.

“It’s moving!” cried the latter presently.

Suddenly the adobe square shifted, slipped out of place, and went thumping to the ledge outside. The boys looked through the opening. Far below them lay the encampment and the river that ran through the gorge. A few women were moving about among the huts, but the boys could see no sign of either the bandits or the horses.

“Let’s get out of here. There’s no one on guard,” remarked Frank. “And I’m going to find some food.”

Now that the key brick was out the boys had no further difficulty. In a few minutes they had cleared away a space that enabled them to leave the cave and emerge into the fresh air of the mountainside.

“If we can only find our ponies we may be able to escape,” said Joe. “What shall we do? Take a chance on going down toward the camp?”

“I’m game. If the bandits catch us, they will put us back in our prison again. But if we keep our wits about us, we shan’t be caught.”

They made their way down the path from the cave mouth, well aware that against the side of the cliff they would be plainly visible to anyone who might chance to be looking that way from the camp below. Here and there grew bushes with berries, and the boys were tempted to strip off the fruit and eat it. They kept each other from doing so, however, mindful of their unfamiliarity with native edibles and their experience with the cactus nectar in the desert.

By the time the boys reached the level just above the river bank they were satisfied that they had not been seen. They hid in the shelter of a huge rock and took stock of their surroundings. The village had been built on an enormous even space between the base of the cliff and a second slope that led steeply to the stream in the gorge. At a little distance a flight of old stone steps ran down toward the water’s edge.

The boys were surprised to see that the cave in which they had been imprisoned was not the only opening in the face of the precipice. It was literally pitted with similar entrances, some large, others small, yet all opening upon terraced trails that eventually led to the water.

“Any sign of the ponies?” asked Frank.

Joe shook his head.

“There isn’t a horse in sight. And where are the bandits? They can’t all be asleep.”

The boys hurried across the open landing to the top of the stairs.

“No use taking the direction of the camp. We’ll be seen,” said Frank.

Suddenly Joe grabbed his arm.

“Duck!” he gasped.

The brothers crouched down on the steps just as a horse and rider came clattering around the side of the bluff where they had been hiding. The man was one of the bandits, but he was in too much of a hurry to give more than a passing glance to the stairway. A moment later he flashed by and rode on.

“We’d better get out of here,” muttered Joe. “It’s a bit too close to the public highway for comfort.”

Frank agreed, so cautiously the boys crept down the steps, which had been carved out of the solid rock and were evidently centuries old—a prehistoric staircase that had survived the wind, the rain, and the footfalls of years.

No one was in sight when the Hardys reached the river. Before them ran a smooth, wide stream about a hundred yards from bank to bank. On the opposite side rose high walls of forest, a veritable jungle of green trees and creepers interspersed with thousands of gay tropical flowers. It was a beautiful scene, and in any other circumstances the boys might have appreciated it more.

Just now their minds were occupied with the problem of escape. And the more they surveyed the situation the greater the problem became. They heard shouts from beyond the bend, and it was evident they came from some of the bandits.

“We can’t escape without the ponies, that’s certain,” Frank said. “Probably they are tethered back of the camp, and if we go that way, we shall be seen.”

“We might follow the river,” Joe suggested. “Perhaps there will be camps farther down where we can hire horses.”

“Hire them! We haven’t any money. And I doubt if any of the natives will lend horses to strangers.”

Just then they heard footsteps on the stone stairs above. The boys quickly hid among the rocks by the river bank.

Two natives came down the steps. One of them was carrying a basket, the other a bundle of cacti. As the boys watched, mystified, the man with the cacti went down to the water’s edge, picked up a stone, and pounded away the prickly spines of the plant.

The other, in the meantime, removed the cover from the basket and a cloud of steam rose into the air. Protecting his hands with a cloth, he took out a rock and tossed it into the water where it fell hissing beneath the surface.

“Yaqui told me about that,” whispered Joe. “That native is throwing hot rocks into the river to ward off the water serpent. It’s one of the superstitions of these people.”

When he had pitched in a few stones, the man with the cacti waded out from shore, dropped the sodden leaves into the water, and began to stamp upon them.

“He’s fishing,” Joe explained. “That’s a species of cactus that acts like a sleeping powder. He’s stamping the juice out of it. Watch.”

After some time the brothers saw a fish floating on the surface. Instantly one of the natives seized it and threw it upon the shore a few feet from the boys. Then a trout floated up, stupefied by the liquid from the cactus. It, too, was gathered in. The Hardys, although they did not know it at the moment, were witnessing a method of fishing that has been used by Mexican cliff dwellers since prehistoric times.

“Not much sport about it,” said Frank. “But I suppose if you want food in a hurry it can’t be beat.”

“Food in a hurry!” groaned Joe. “Say, I have an idea.”

In a moment he was moving cautiously toward a bush and in an instant had broken off a long twig. Secreting himself again near Frank, he held the point of his newly contrived rod before him and speared one of the fish. Then slowly he drew it back.

“Clever, Brother,” said Frank. “But I never could eat a raw, poisoned fish.”

“It is not poisoned,” replied Joe. “Only sleepy. And anyway, its flesh is all right.”

After this remark he reached out his “pole” once more and caught another trout. As fast as the natives threw their fish upon the bank, just so fast did their catch disappear. In the meantime Frank was tearing off pieces of the meat, and after managing the first mouthful declared the food was not bad.

“They’re coming up now,” announced Joe, as the natives prepared to leave the stream.

With bated breaths the Hardys lay flat on the ground behind the rocks as the fishermen approached. In a moment there was a piercing scream from the man in the lead as he discovered there were no fish where he had thrown them. Raising his hands above his head he began to jump around and repeat what was evidently an incantation. This was taken up by the second native when in consternation he learned of the situation.

Presently the two tribesmen looked wildly about them, then dashed up the stone steps. The Hardy boys could only guess that the superstitious natives figured some angry evil spirit had snatched away their catch.

“Too bad,” said Frank with a chuckle, “to fool those poor people, but they have other food. Here, help yourself, Joe.”

Barely had the natives disappeared when the boys again heard people talking, so they remained in hiding. One of the voices was familiar. The man was speaking in Spanish, and Frank was sure he had heard the tones before. He looked at his brother in amazement.

The boys peered out from behind the rocks. There, not ten yards away, was Pedro Vincenzo!

There was no mistaking the figure of the swarthy Mexican, as he stood in the bright morning sunlight, talking earnestly to a companion who was unmistakably a half-breed. This was the native who had questioned Yaqui about the Hardy boys in the squatter’s cabin, the same fellow who had come to Pedro Vincenzo’s assistance and knocked Frank senseless in Señor Marcheta’s garden.

Spellbound, the boys watched the man who had led them this long chase into the mountains of Chihuahua. They had found Pedro Vincenzo at last, but they were helpless. They could do nothing but remain in hiding and listen.

It was plain that Pedro was angry about something. But he was talking in a language that the Hardy boys did not understand. He was violently berating his companion, who listened meekly. In the course of the tirade there was one word that Frank and Joe did catch repeatedly.

The word was “Hardy.” A little later they heard “Señor Hardy.”

Frank saw that Vincenzo was smiling cruelly. Whatever the man was saying, it appeared to afford him great satisfaction, for he extended his hand, then closed it tightly as if he were squeezing something in his grasp.

It seemed to give great satisfaction to his companion as well, for the man slapped his knee and laughed.

“I’m very worried,” Frank whispered. “Dad——”

The Hardy boys could not understand what Pedro Vincenzo and his satellite were saying, but they could guess. The two men were talking about Fenton Hardy, and from their actions there was no doubt but that they hoped soon to have the detective in their power, if they had not done so already.

What did Vincenzo know? What was the reason for the glee of the two conspirators? Frank and Joe were not enlightened further, for the two men moved on down the river bank past the rocks, and then ascended the flight of steps leading to the ledge above.

“Well,” said Joe, when the pair had vanished, “there’s our man. What are we going to do about it?”

“There are several things we might do,” replied Frank.

“For instance?” asked Joe.

“Let’s shadow him.”

“Vincenzo? Now?”

“Why not?”

“It’s too dangerous,” Joe objected. “He’s on the upper level now, with all the natives to help him if he catches us.”

“I don’t care,” said Frank. “He’s the man who can lead us to Elmer Tremmer if he is alive, and that’s our reason for being in this country. Come on.”

Cautiously the boys followed the wily Mexican and his cohort. Luck was with them, for no one else appeared and the men ahead were in too much of a hurry to look back.

“Down!” suddenly commanded Frank, who was climbing the steps ahead of his brother.

Instantly the two lads huddled under an overhanging cliff.

“Pedro stepped into a cave just above us,” whispered Frank. “The other fellow went on ahead.”

For fifteen minutes the Hardys waited. Then they saw the man they were after emerge from the cave and ascend once more.

“After him!” said Frank.

“No,” replied Joe. “I’m going to investigate that place Vincenzo just came from. He’s heading for the camp and we don’t dare follow him. I want to have a look inside that cave, anyway.”

For several minutes after entering the enclosure the boys could see nothing. As their eyes gradually became accustomed to the semi-darkness, they began to look around and at first were disappointed that apparently the cave was empty.

Then suddenly Joe pointed.

“The mark!” he exclaimed. “The mark of Pedro!”

There it was. The burning fagots with the letter P in the flames scratched into the wall.

“Wonder if it means anything,” commented Frank, running his hands over the surface where the symbol had been crudely sketched on. “I’d like to bet—oh!”

The boy’s slender fingers had found a slight depression and in a moment were pulling at a section of the side. A good-sized stone came away, revealing a deep niche.

Frank reached in quickly, and to the surprise and delight of the boys drew forth an oblong box wrapped in a newspaper. Rushing to the cave entrance, they were amazed to find the sheet to be printed in English.

“The—the Bayport Star,” exclaimed Joe, as he noted the items more closely. “And the date—the date is the day when we started on this mystery!”

The brothers were so excited at their find, and for a few minutes so struck with a wave of homesickness as they read names and events so familiar to them, that they failed utterly to see the full significance of their discovery.

Frank was the first to recover composure and realize the importance of the matter.

“Joe, I think we’ve stumbled upon something valuable,” he said. “Perhaps the contents of this box came from Bayport, too.”

Quickly the boys opened the wooden chest which was branded with Pedro’s peculiar insignia, and saw rolls and rolls of American bank bills of large denomination, held together with elastic bands. With them was a notation in Spanish which the Hardys figured out to indicate that the money was Vincenzo’s share in the sale of the fake Rio Oil Company stock.

“So the man had no money to pay his helpers!” said Joe in disgust. “That fellow is several kinds of a scoundrel.”

“These bills don’t belong to him by rights, I’m sure,” was Frank’s rejoinder. “I suggest we hide this box in another cave, and then tell the authorities about it later.”

“Fine idea,” agreed Joe.

Together the boys scouted around a bit, watching carefully so they would not be seen, and at last found a deep crevice which seemed to suit their purpose. Into it they pushed their valuable find, and made a clear mental note of the location.

“Score one for us,” said Joe. “Now to escape from this place and get some help.”

“We can’t go any farther up the steps. It’s too risky,” Frank said. “I think we had better work our way along the river bank until we’re a good distance from the camp. Then we may be able to find our way to the main trail.”

As this seemed to be the most feasible plan, the brothers emerged from their hiding place and went down the stone stairway. Then they headed for the shelter of some rocks farther down the shore. They had gone no more than a few steps, however, before Joe uttered a yell of alarm and leaped wildly to one side.

A harsh warning rattle sounded. Right in the boy’s path a huge snake was coiled in the sunlight. It struck viciously, uncoiling itself to its full length in the twinkling of an eye. Fortunately Joe had caught sight of the rattler just in time, and sprang out of reach as the wicked head flashed past his foot.

Frank snatched up a heavy rock and hurled it at the snake. The reptile gathered itself into a coil again, hissing evilly. The lad’s aim was bad, and the rock clattered harmlessly to one side. Then Joe hurled a stone, striking the creature in the back. Thereupon the rattler lashed out once more, but in a moment went writhing swiftly toward the rocks.

This had taken only a few seconds, but Joe’s shout of alarm and the subsequent noise on the rocks had not gone unheard. From the ledge above came a surprised yell. When the boys looked up they saw a native standing at the top of the stone steps.

“Run!” exclaimed Frank.

The Hardys went racing down the river bank. Behind them the half-breed was already raising the alarm, and when Frank glanced back over his shoulder he saw half a dozen of the outcast Indians leaping down the steps in pursuit.

Frank and Joe bolted around an outcropping of rock. To their dismay, they found that the river bank became very narrow at this point, sloping directly toward the water in a steep declivity from the ledge above. They went scrambling up the slope, grabbing at bits of rock and tiny bushes to aid them. In their hearts they knew it was useless. They could never hope to outdistance the fleet-footed natives.

The man who had first seen them was now close behind. Yelling with triumph, he began to ascend the slope in pursuit. At the same time the boys could see other Indians running along the ledge above to cut off any way of escape at the top of the bank.

“No chance,” said Joe bitterly. “They’ve caught us.”

With natives close at their heels and others waiting for them at the head of the slope, the boys found escape impossible. Wearily they pulled themselves up to the ledge, where they were instantly seized by three dark-skinned Indians, who bound the arms of the unfortunates behind their backs.

There was a great deal of chattering and loud talking. The man who had discovered their escape came up grinning with pride, evidently thinking very well of himself.

“If it hadn’t been for that rattlesnake,” muttered Joe, “we might have got away.”

They were marched back to the camp in disgrace. Frank was hoping that Pedro Vincenzo would make an appearance, but neither he nor his companion were anywhere to be seen, although all the natives and some of the bandits gathered around to learn the cause of the disturbance.

One of the bandits came up and consulted briefly with the natives. Then he gave a curt order and the prisoners were hustled away.

This time they were not taken back up the trail to the cave in the face of the cliff. They were brought to a niche on the lower level, much nearer the camp. It was a dismal little hole like a dungeon. As soon as the boys had been thrust roughly through the entrance, a native armed with a revolver took up his position a few yards from the opening and squatted down in the sun.

The boys were now in a worse plight than ever; under close guard, with no further chance of escape, their hands bound so tightly that they had little freedom of movement. After an hour or so their arms were aching. Frank called out to the guard.

“You don’t need to keep us tied up. Cut the ropes. We won’t get away.”

The man stared at them blankly. As well as they could the boys tried to make him understand, yet the fellow was either stupid or he had no intention of cutting their bonds, for he simply turned his back and paid no further attention to them.

“I’m just beginning to remember that we haven’t eaten this morning,” said Joe miserably. “I’m as hungry as a bear.”

“Surely they don’t intend to starve us. Of course, it’s our own fault that we weren’t on hand at breakfast time.”

Frank called to the guard again and tried to make further signs indicating that they were hungry. But the man merely laughed and turned away again.

Hours passed. The boys were in the depths of wretchedness. Another native came up and replaced their former guard. This man seemed of a more friendly disposition, for he came into the cave, took a knife from his belt and cut the ropes, apparently realizing that it was needless cruelty to keep the prisoners tied up while under close supervision.

Again Frank and Joe made signs to indicate their hunger. Although the man evidently understood, he shook his head, pointed down to the camp, and burst into a lengthy explanation which the boys could not interpret. They did gather, however, that he did not dare get them anything to eat.

“I guess he has to obey orders,” Frank said, stretching his arms, which were stiff and sore. “Maybe we’re lucky we weren’t shot for trying to escape.”

The day wore on slowly. The guard was sympathetic enough to bring them some water. Although they were made to suffer from hunger, they were not forced to endure the added torture of thirst.

“I wonder where Yaqui is now,” said Joe reflectively.

“Halfway home, probably. I hope he tells Señor Marcheta what has happened to us.”

“It’s strange the natives haven’t been making a fuss about his escape.”

“Perhaps he didn’t escape after all,” said Joe significantly. “He may have been killed trying to get away, for all we know.”

The boys spent a miserable day. When they left Bayport, excited over the prospect of an adventurous trip to Texas, they had not bargained for anything like this. As night came, their discouragement became greater. A new guard appeared on the scene, bringing with him a substantial supper which he ate on the adobe platform outside the entrance, smacking his lips over every mouthful. The boys tried to persuade him to share the food with them, much as it hurt their pride to do so, but he shrugged his shoulders and continued to gormandize.

“Greedy brute!” said Frank.

“I feel absolutely hollow.”

When the guard had finished his supper he paced up and down before the entrance to the cave. After a while Frank and Joe heard a shout, which the sentinel answered. A moment later he came to the doorway and beckoned to them.

“Supper time!” exclaimed Joe gleefully.

“Maybe.”

The boys went outside. Up near the camp they could see a great fire blazing, and in the light of the flames they saw figures moving to and fro. Then a drum began to beat monotonously.

Frank gulped.

“I hope they don’t intend to burn us at the stake!”

The guard growled an irritable command and thrust them ahead. The flickering flames, the shifting figures in the firelight, the monotonous pounding of the drum created a wild and savage effect. A group of natives sitting just beyond the circle of radiance were chanting solemnly.

“It must be some sort of ceremonial dance,” remarked Joe, with as much confidence as he could muster.

Frankly, he did not like the looks of the situation at all. What barbaric rites might be practiced here in the heart of the mountains he did not know, yet he was prepared for anything.

A tall native with his head wound about in colorful bandages and his face painted horribly, leaped out from the circle and motioned to the guard, who brought the prisoners over immediately. No one else paid any attention to them. The Indian with the painted face was evidently a medicine man, for he appeared to be in full charge of the ceremony, directing the natives who danced wildly around the fire and continued their droning chant to the beating of the drum.

Frank’s attention was caught by a raised platform not far away, where a small figure was seated in state watching the performance. The man was enveloped in a gay blanket and had a headband about his hair. Though he was dressed as a native, Frank saw at a glance that the man was neither a Mexican nor an Indian.

That man! In this place!

Frank nudged Joe vigorously and indicated the person on the platform.

At that moment one of the half-breeds threw a great heap of fagots on the fire. They ignited with a roar and the flames leaped high into the air. The whole face of the cliff was illuminated with a ruddy glow. So intense was the light that the Hardy boys could now see the white man’s face clearly.

A simultaneous cry of recognition broke from their lips, although the smooth shaven individual was changed from the last time the Hardys had seen him.

“Elmer Tremmer!”

In spite of their surprise and the gravity of their position, the Hardy boys almost laughed aloud when they saw the missing witness, the former Bayport bookkeeper, sitting in state in his outlandish garb.

Elmer Tremmer had always been a meek, inoffensive man inclined to rusty black suits and linen collars, the soul of respectability and conventionality. To see him in this wild place, with a blanket about him and a band around his gray hair, was almost too ridiculous. From the expression on Elmer Tremmer’s face he did not seem to be enjoying himself; he appeared to realize that he was quite as much out of place here as one of the natives would have been in a Bayport office.

“Elmer Tremmer, and in a box seat!” exclaimed Frank.

“We must talk to him. He doesn’t seem to be a prisoner. If anyone can get us out of this jam it will be he,” Joe declared.

“He hasn’t seen us yet.”

Frank looked around at the guard. But that worthy was so absorbed in watching the ceremonial of the dance that he appeared to have forgotten his prisoners altogether. In a moment the two boys slipped away from his side and vanished into the shadows.

There was so much confusion as one native after another joined the ring of figures around the fire, that the Hardys were able to make their way close to the platform without being noticed.

Elmer Tremmer, his arms folded, gazed solemnly down at the crowd.

Frank knew that any open attempt to attract the man’s attention might be disastrous, so the brothers edged their way as near the platform as they dared, and pretended to be absorbed in the spectacle before them. Frank had, at one time, tried to learn the tricks of ventriloquism and had taken lessons in the art from a famous vaudeville artist who was a close friend of Fenton Hardy. This practice now stood him in good stead.

Gazing straight before him, and without moving his lips, he said clearly:

“Mr. Tremmer!”

Out of the corner of his eye he saw the figure on the platform start violently. The man looked up, then all around him, his face a study in bewilderment. This was the last place in the world where the fugitive bookkeeper might have expected to hear his name called aloud.

“Look down,” said Frank.

Tremmer obeyed. Then his eyes opened wide as he saw the two American lads almost at his feet.

“Who—who are you?” he stammered weakly.

“We’re the Hardy boys from Bayport,” Frank told him.

Elmer Tremmer’s expression became instantly suspicious.

“Bayport!”

“Yes. We’d like to talk to you.”

“Not here,” muttered Tremmer hastily. “Not here. They—they may be watching us. It’s dangerous.”

“Don’t you want to get out of this place? Perhaps we can help you escape.”

“I’ll come to see you tonight,” the man muttered. “Don’t talk here. I’ll come to your cave.”

“When?”

“As soon as I can get away. Midnight, probably. But don’t talk any more now. Don’t let on you know me.”

Tremmer was evidently very much frightened, so the Hardy boys quietly withdrew and returned to their guard, taking up their positions at his side. The man, still staring at the dancers, had not even noticed their absence.

Frank plucked the guard’s sleeve and made signs that they wished to go. He was evidently annoyed at having to miss the rest of the spectacle, but went back to the cave with them, grumbling all the way. They tried to persuade him to get them some food, but the man was now in a bad tamper and their request was ignored.

Back in the cave the boys sat down to await the coming of Elmer Tremmer, and to make plans. If they could only escape from the cañon with the fugitive witness, their mission to Mexico would be a success.

“He seemed to be scared stiff,” remarked Frank. “I wonder if he is a prisoner after all. If they have him under guard he won’t be able to come here.”

“Perhaps he isn’t closely watched.”

The moon rose higher in the sky. The boys peered out of the cave. To their surprise they found that the guard had vanished.

Frank chuckled.

“I guess he thought we were asleep and figured he might as well go down again and watch the dance. He didn’t like it very much when we made him leave right in the middle of the performance.”

A few yards down the trail they heard a light footstep. As the boys watched, a shadowy figure came moving quietly along the wall of rock.

“It’s our guard coming back,” whispered Frank.

“The guard wouldn’t move that quietly. It must be Tremmer.”

Swiftly and silently the man came nearer. Then with a few quick strides he reached the mouth of the cave.

“Yaqui!” cried the boys.

It was indeed their erstwhile guide. He was breathing heavily, as if he had traveled a long distance. Without a word he plunged into the cave and flung himself down on the floor, panting breathlessly.

“Yaqui, where did you come from? Where have you been?” the brothers demanded anxiously.

“Went for help,” he gasped. “Got horses. And food.”

He gestured weakly toward a bag slung across his back.

Frank and Joe were overcome with joy and not a little ashamed of the suspicions they had entertained that morning. Yaqui had not deserted them after all. How many miles he had traveled that day they did not know, but it was plain that his great strength was almost exhausted.

The boys opened the bag of food and ate hungrily, though sparingly, realizing that the food might have to last them for a long while. The Indian refused to eat.

After a time he recovered sufficiently to tell them something of his adventures. He had made his way down the back trail on foot until he had found tracks that led him to a small farm in the foothills. There he had succeeded in borrowing horses and obtaining food.

While the Yaqui, in low tones, was telling his story, the boys again heard footsteps on the trail leading to the cave.

“Quick! Hide!” they urged the Indian. “It may be the guard.”

Yaqui promptly concealed himself behind a niche of rock at the back of the cave. The boys waited as the cautious footsteps came closer. Then Elmer Tremmer sidled into their prison.

“I can’t stay very long,” he whispered. “If Vincenzo misses me he’ll suspect something.”

“Is Vincenzo in the camp now?” asked Frank.

“Yes, of course,” returned Tremmer. “Oh, dear,” he added mournfully, “if I’d known it was to be like this I don’t believe I should have ever left the States.”

“But why did you leave?” Joe asked.

“You know well enough,” returned Tremmer. “I went away because I’d have been sent to prison if I had stayed. That’s why you’re here. You want to bring me back. But I’m not going back,” he declared. “Even this is better than being in jail.”

“Then you came of your own free will? You aren’t a prisoner?”

“I’m not supposed to be a prisoner, though I might as well be one,” replied the former bookkeeper. “It was an unlucky day for me when I took that job with the Rio Oil Company, I tell you. Vincenzo promised me I’d have a wonderful life if I’d come to Mexico with him. Now, here I am in this miserable camp in the mountains. Nothing very glorious about it.”

“Vincenzo told you that you’d be sent to jail if you stayed in Bayport?” inquired Frank.

Tremmer nodded. “He said the authorities were preparing to arrest me. You see, being the bookkeeper of the firm, I should have known that there was something crooked about the business. He says I’m legally just as much to blame as any of them. So I ran away.”

“Vincenzo was lying to you,” Joe said. “The authorities wanted you as a witness against the Rio crowd. That’s why Vincenzo talked you into going away.”

“That’s your story,” answered Tremmer suspiciously, “but I know different. You’re trying to talk me into going back with you. Then the moment I step on American soil you’ll have me arrested. I’m not such a fool as all that. Fenton Hardy has trailed me ever since I left Bayport, and now you’re trying to make me fall into his trap. No, sir!”

The boys had expected any attitude but this. Patiently they argued with the man, aggravated by his stupidity. But Elmer Tremmer had evidently been thoroughly frightened by Vincenzo, and resolutely refused to return to Bayport.

“This isn’t much of a place,” he said, “but at least it isn’t jail.”

“Don’t you believe we’re telling the truth?” demanded Frank. “Don’t you trust us?”

“No,” returned Elmer Tremmer promptly. “You’re detectives and you are trying to arrest me.”

Half an hour of argument failed to alter the man’s decision. He was convinced that his only safety remained in staying with Pedro Vincenzo. Nothing the boys could say would convince him otherwise. Finally, in desperation, Joe exclaimed:

“Well then, if you won’t come back to Bayport with us, surely you’ll help us get away from here, won’t you?”

In the moonlight that shone through the cave entrance they saw that Elmer Tremmer’s weak face looked frightened. He shook his head.

“No. I couldn’t do that. It’s impossible.”

“But why?” they asked, almost dumbfounded by his refusal.

“You’re not getting away from here if I can help it. If you ever reach the city you’ll tell everybody where I am. Besides, I don’t dare make Vincenzo angry. He could turn me over to the police in a minute if he wished.”

“Do you mean to say you won’t help us?”

“I don’t want to go to jail. And that’s what will happen if I help you escape from here,” declared Elmer Tremmer stubbornly.

The boys pleaded with him desperately, but Tremmer was not to be moved. He had a vein of obstinacy in his makeup that was hard to break. Yet back of everything was his fear that he would be taken to the States and sent to prison because of the Rio Oil frauds. Over and over again Frank and Joe tried to convince him that his fears were groundless and that he was playing into the hands of Pedro Vincenzo, but Elmer Tremmer refused to listen.

“It’s all a trick!” he said. “Just a trick to get me back. I’m too smart to be fooled.”

“Smart!” said Frank. “Vincenzo has fooled you from the beginning.”

“Maybe. Maybe,” replied Tremmer. “But he hasn’t tricked me into jail yet, and that’s what you’re trying to do.”

“You’re a fine specimen if you won’t help us escape from here, that’s all I can say,” Joe told him angrily.

Tremmer got up and moved toward the cave entrance.

“Can’t help it. Can’t help it,” he said. “I have to look out for myself.”

Then he scuttled out into the night.

“What a pal!” exclaimed Joe in disgust. “I’m ashamed to think that a man like that comes from my own home town.”

“He’s stupid and weak——”

“And scared pink.”

“Yes, he’s scared. That’s the big trouble. Vincenzo has filled him up with a lot of lies. If Tremmer were as smart as he thinks he is, he would have seen through the scheme long before.”

The tramp of heavy footsteps outside the cave silenced them. When they looked out they saw that two sentinels had been posted at the entrance, one on either side. Frank whistled softly.

“The guard has been doubled. Now, I’ll just bet that’s some of Tremmer’s work.”

“He not only refuses to help us escape, but he’s going to make mighty sure that we won’t do so ourselves,” grumbled Joe.

Yaqui emerged from behind the niche where he had been hidden.

“Don’t worry,” he advised softly. “I think everything be all right.”

Thereupon he sprawled on the floor, pillowed his head on one arm, and fell fast asleep.

“It doesn’t seem to worry him very much,” murmured Frank.

“He knows it won’t do him any good to worry. We may as well go to sleep, too, and try to forget it all.”

So, following the philosophic example of the Indian, the boys also were soon asleep.

They were awakened in the morning by a disturbance at the mouth of the cave. Frank sat up, blinking, and saw a tall figure come striding through the entrance. Quickly he reached over and shook Joe.

“So!” observed their visitor. “The young detectives have slept well, I hope?”

The man was Pedro Vincenzo. He stood grinning unpleasantly at them, a smirk of triumph on his swarthy face.

Joe sat up and rubbed his eyes. When he recognized Vincenzo, he became fully awake.

“Just the man we wanted to see.”

The Mexican looked about the cave.

“Not very luxurious,” he said. “But a hard bed and plenty of fresh air will hurt no one.” Then his manner changed. “Well, you brats!” he snarled, “I hope this will teach you to think twice before you try to interfere with me.”

“It’ll teach us to be more careful, perhaps,” replied Frank with spirit. “I suppose you know you’re letting yourself in for plenty of trouble, Vincenzo.”

The man laughed harshly.

“You cannot scare me,” he said. “I am master in this place.”

Frank and Joe had been frightened lest Vincenzo should discover the presence of Yaqui. Now they found to their surprise that the Indian had disappeared. How and when he had vanished they did not know.

“How long do you intend to keep us here?” Joe asked.

“I have plans of my own,” returned their captor. “I have a little deal under way. I need that fool Tremmer, and you were trying to take him away from me. When I’ve finished with him—well—who knows?”

“If you have a deal under way I’ll bet it’s a crooked one,” Frank said warmly.

“Mind your own business,” growled Vincenzo. “You’ll stay here until I’m ready to let you go. And you won’t be released until Tremmer and I are miles away. But remember—if you try to escape sooner it will be that much worse for you. I’ll turn you over to the natives in charge of the Ceremonial of the Fire. Do you know what that will mean?”

His face was ugly with malice and cruelty.

“Don’t take a chance on being branded with the mark of the P and the fire!” warned Vincenzo. “You wouldn’t want to go back to your friends in Bayport with that sort of decoration on your foreheads. Besides, it’s said to be very painful.”

“We’re not afraid of your threats,” Joe answered.

“Brave boys!” jeered Vincenzo. “You’re not so clever now, are you? And you won’t think your father is so clever, either, when he’s thrown in here to keep you company.”

“Our father is worth twenty of you.”

In the distance they heard a shot. Pedro Vincenzo looked up, startled, and strode to the entrance. As he said something to the guard, they all heard another shot, followed by a series of wild yells.

“Better hurry,” advised Frank. “Perhaps the soldiers have come to clean up this den of yours and set us free.”

“Soldiers! Bah!” exclaimed Vincenzo.

It was plain, however, that he was puzzled and nervous.

“You might leave us something to eat,” suggested Joe. “I hope you don’t intend to starve us to death.”

“You’ll get food. All in good time. It won’t hurt you to go hungry for a day or so.”

Then the scoundrel strode hastily out of the cave. In a moment there was a slight rustling sound. The boys looked around, and saw Yaqui emerging from behind some rocks.

“You heard what he said?” asked Joe.

Yaqui nodded.

“He talks big. But he is not as safe as he thinks. Already the natives are beginning to grumble.”

“How do you know?”

“I have heard the guards talking. They say Vincenzo has made many promises but has not kept his word. He said he would pay them if they helped him. They are wondering when they are going to see the money.”

“They’ll never see it,” replied Frank. “The fellow is a crook. I can’t figure how any man can be as dumb as Elmer Tremmer, to be fooled by that sort of talk.”

“I don’t feel very much like trying to escape, just the same,” observed Joe. “I’m not eager to be turned over to the natives for branding.”

Yaqui then explained that the ceremony the boys had witnessed the previous night was part of the regulation ritual of the Sun Worshippers, and that Pedro Vincenzo had doubtless introduced a few ideas of his own, among them the branded sign of his initial in the fagot fire.

“It is—what do you call it?—his mark.”

“His trademark,” said Joe. “Well, I’m not looking forward to having it on my forehead.”

As they talked, the three heard more shots and sounds of a disturbance near the main camp. The guards, too, seemed to be excited, for they were crouching together and staring down in the direction of the river.

“There’s something going on,” Frank said, puzzled. “I wonder what’s happening.”

At that moment a native came running up to the entrance of the cave. He talked excitedly to the guards. Yaqui crept closer to the opening so that he could hear what was being said. In the distance the boys heard a burst of gunfire, followed by shouts and screams.

Whatever information the newcomer brought to the guards, it proved to be important. One of the men threw aside his gun and would have hurried away, had not the other argued with him and held him back. The native who had run up to the entrance of the cave went away again hurriedly and the two guards launched into a feverish dispute.

Yaqui came back to them.

“A revolt!” he whispered eagerly. “There is trouble in the camp.”

“What’s up?” the boys demanded.

“The natives are tired of waiting for their pay. Tremmer is stirring them up to get rid of Vincenzo. Some of them are leaving the village and crossing the river with Tremmer.”

“Good!” cried Frank. “If their forces are split it will make it easier for us to try a get-away.”

“Vincenzo is hoping to hold his men together. He is promising them anything they want—but he says he has no money, and nothing else will satisfy them.”

“I didn’t realize Tremmer had it in him,” Joe declared. “He must have done a lot of thinking after he left us last night. Perhaps at last he realizes the truth.”

The uproar was growing in volume. Evidently Vincenzo was having a hard time keeping the natives under control.

The boys’ guards wanted to be in the thick of the disturbance. As the racket from the river bank grew louder and louder they hastily left their posts and dashed down the trail without another thought for their prisoners.

“Now’s our chance!” cried Joe gleefully. “Let them fight all they want to. We’ll get away from here. Yaqui, where are the horses?”

“About a mile up the trail,” he answered. “But do not be too hasty. Let us see what is happening.”

They emerged from the cave, and came out onto the level adobe platform at the entrance. It was evident that Elmer Tremmer’s revolt was at least partly successful. A dugout canoe was crossing the river with half a dozen natives, while another was just landing on the other side. Even at that distance the boys could distinguish the figure of the missing witness, shouting orders to the men as they landed.

On his side of the stream Vincenzo was vainly trying to hold the rest of the tribe in check. Some of them were clambering into a canoe preparatory to deserting to Tremmer’s crowd. The outlaw was striding up and down, waving his arms wildly as he shouted at the men. Everything was in confusion. Many of the women were packing up their meagre household effects. Occasionally someone would fire a rifle into the air, and a native across the river would answer with a shot.

Suddenly Vincenzo ran down to the water’s edge and collared one of the men who was stepping into the dugout. The man struck back at him. Two others leaped out of the canoe and tackled Pedro, whereupon some of the loyal natives rushed down the bank to protect their leader. In an instant a real fight was in progress. One of Tremmer’s canoes started back across the stream. At the same time five of Vincenzo’s natives leaped into a dugout and paddled out to meet them.

The two canoes came together with a crash in midstream. There were wild yells as Vincenzo’s party went over into the water. The others, being more expert as canoeists, held their craft upright. In the meantime, the fight on shore was becoming general, with the deserters getting the best of it.

Vincenzo himself was hurled into the water. He emerged spluttering just as Tremmer’s party thrust their craft away from shore. Farther up the bank a few more natives were sneaking off to join the others on the opposite side of the river, evidently having no desire to stay with a lost cause.

Tremmer’s little army was growing. Only a handful of natives, including the women and children of the camp, remained loyal to Vincenzo.

“He’s beaten!” cried Frank. “Come on, Joe. Come on, Yaqui. Let’s find those horses.”

They went scrambling down toward the main ledge above the river. Vincenzo, his clothes dripping with water, was yelling threats at the party on the opposite bank and trying to persuade his men to return to him.

One of the natives who had refused to join the insurgents suddenly caught sight of Yaqui and the Hardy boys. He uttered a yell of alarm and grabbed his leader by the sleeve.

“After them!” roared Vincenzo.

“Run!” shouted Joe.

Yaqui could have escaped. He was as fleet-footed as a deer and could have outdistanced the pursuers with ease. Yet he would not desert his young companions. Frank and Joe strained themselves to the utmost, but when they looked back they saw that three of Vincenzo’s men were swiftly overtaking them. Within a hundred yards the chase was over.

One of the natives flung himself at Frank in a flying tackle and brought him down. Another leaped at Joe when he stopped to help his brother. A third presented a rifle at Yaqui’s head and ordered him to surrender.

The Hardys struggled vigorously, but they were no match for the natives. In a few moments they were led ingloriously back to camp and brought before Pedro Vincenzo, who glared at them malevolently.

“Didn’t I warn you of what would happen if you tried to escape?” he snarled. “Didn’t I say you’d be branded?”

“I think you have enough trouble on your hands without worrying about us,” Frank reminded him. “Tremmer seems to have turned the tables on you pretty neatly.”

Vincenzo flushed darkly. He had only about half a dozen natives at his disposal, all the others having gone across the river to Elmer Tremmer’s side. He knew that he could not even bank strongly on the loyalty of those who had remained. It was only too true that the fugitive bookkeeper had turned the tables on him. He was beaten, and he knew it.

“The natives are fools,” he growled. “What can Tremmer do for them? They’re crazy to listen to the fellow.”

“They didn’t have much sense when they listened to your promises, either,” chirped Joe.

“That’s enough!” snapped Vincenzo in an angry voice. Then he turned and called out in a loud tone, “Come back, Tremmer! Let’s talk this over.”

But Elmer Tremmer, now that he was out of Vincenzo’s power for the moment, seemed to have gained new courage. He was standing on the opposite river bank in the attitude of a man who has won an unexpected victory, and has not yet decided how to proceed.

“If there’s any talking to be done,” he called back, “I’ll do it!”

“That’s right, Mr. Tremmer!” cheered Joe, “Don’t let him bluff you.”

Vincenzo silenced the boy with a look.

“What do you want, then?” he called back to Tremmer. “What are your terms?”

“I want my freedom!”

“But you are free,” cried Vincenzo. “You’ve always been free. Haven’t I treated you well ever since we left the States?”

“I’ve been no better than a prisoner, and you know it,” Tremmer answered. “You’re afraid to let me out of your sight for fear I’ll go home.”

“Send my men over to me,” Vincenzo shouted, “and you can go wherever you wish.”

But Tremmer was not to be trapped by this promise.

“Then you’d put them on my trail and have me brought back,” he answered. “No, that won’t do. I’ll make a bargain with you.”

“What’s your bargain?”

“I know where Fenton Hardy is and I can turn him over to you,” came the astonishing reply.

Frank and Joe gasped with amazement.

“The detective!” shouted Vincenzo.

It was evident that he found the bookkeeper’s statement hard to believe.

“Let me go and you can have him,” the other declared.

The Hardy boys did not know what to think of Tremmer’s extraordinary proposal. At first they felt the man was just bluffing, and bargaining for his own safety. On second thought, however, they saw that Tremmer could not hope to win release by a bluff alone. He would have to make good, otherwise Vincenzo would follow him.

“If you know where Fenton Hardy is,” cried Vincenzo, “produce him. If you send him here you won’t be followed. If you fail, I’ll hound you to your death! And I’ll brand these innocent countrymen of yours. These Hardy boys!”

Tremmer spoke to some of the natives. Three of them struck out into the bush along the river bank, and a few minutes later appeared on a high level, making their way up the opposite wall of the cañon. Then Tremmer himself, accompanied by another native, set out behind them.

“Remember!” shouted Vincenzo. “If Hardy isn’t in this camp within an hour I’ll be on your trail.”

As the boys watched Tremmer slowly make his way up the cañon wall their hearts sank. They had found the missing witness, only to lose him again. Their mission had failed completely.

Their own plight was worse than it had ever been, for it was certain that if Fenton Hardy should not appear Vincenzo would wreak vengeance as he had threatened. Moreover, it was impossible now for the lads to try to escape. They must wait in case their father should come. Every chance to foil Vincenzo had been cut off.

“Every chance but one,” said Frank to himself.

Then he whispered his idea to Joe and the latter shook his head in agreement. Together they looked around for Yaqui, who during the talk had become separated from them. While Pedro was addressing the men on the opposite shore, evidently exhorting them to return to his leadership, the Hardy boys found their Indian guide.

“Yaqui,” said Frank, “we mustn’t lose Tremmer. My brother and I do not dare leave here because our father may come.”

“Do you think,” asked Joe excitedly, “that you could slip away and follow Tremmer?”

The Indian glanced around and nodded. The boys grasped his hands in thankful appreciation. As he moved off, Frank gave him a final instruction which Joe could not hear. The latter knew, however, that his brother was very much like his father, and never missed an opportunity to work out a problem down to the slightest detail.

A moment later Yaqui mixed unobtrusively with the few men nearby. Then the Hardy boys saw him make his way slowly and quietly down the river bank. He vanished around a bend in the stream.

Shortly thereafter they saw a head appear above the surface of the water some distance down the stream. The Indian was swimming across the river. If any of the natives saw him they did not cry out, perhaps thinking that it was one of their own number deserting from Vincenzo’s ranks. Frank and Joe saw a sleek brown body emerge from the water and vanish swiftly into the undergrowth. Yaqui was on Elmer Tremmer’s trail.

Vincenzo was not successful in persuading the deserters to return. In spite of all his arguments the natives decided to wait a while. They wanted to know if Tremmer would keep his word and send the white man back to Vincenzo.

“Take those boys to the cave,” snarled Vincenzo suddenly. He was in a bad temper. “See that they’re well guarded. If Tremmer doesn’t keep his promise I’ll make them suffer for it.”

It was then that the outlaw noted the absence of Yaqui.

“Where’s that other fellow?” he demanded. “Where’s the Indian?”

The guards looked around blankly for Yaqui. Vincenzo was furious.

“He escaped! Right under your noses! Look for him. Bring him back.”

The natives scattered and made a great pretense of conducting an industrious search for the fugitive, yet they had not the faintest idea where to look. Frank and Joe were hastily bundled off to their cave, where an armed guard took his place in front of the entrance.

“I’ll bet Tremmer won’t get very far out of Yaqui’s sight,” said Joe after a time.

“Do you think Tremmer really knows where Dad is?” ventured Frank.

“If he does, it will be easy enough for him to send our father straight into a trap. He’ll tell him where we are, and when he comes for us Vincenzo will be here to capture him.”

“And in the meantime Tremmer will be legging it away to goodness knows where.”

“Was Tremmer lying? That is the question,” said Joe anxiously.

“He didn’t have enough imagination to think up a story like that,” Frank decided. “That’s why I believe there is something to his claim that he knows Dad’s whereabouts.”

“Vincenzo gave him an hour. He didn’t say he would need more time. If Dad is in this part of the country at all he can’t be far away.”

A little dog just then came scampering up to the mouth of the cave, nosed suspiciously about the feet of the guard, and poked an inquisitive head into the entrance. It was a Mexican hairless, of the same breed as the dog Vincenzo had given the boarding house keeper in Bayport.

“We promised we’d try to get Mrs. Smith another dog,” said Joe, trying to appear calm, although his spirits were in a turmoil.

He whistled softly, and the little animal ventured inside. It was very shy, however, and when Joe tried to pat its head the dog drew back quickly.

“I’d like to collar that pup and take it home with me,” Joe said.

“If we ever get there,” Frank reminded him mournfully.

His brother crept toward the animal, but it suddenly retreated and began capering around the cave entrance, barking furiously. Again and again Joe tried to coax it back. Finally he conquered its fears, and the dog crept forward again until Joe was able to scratch its head. A moment later it licked the boy’s face and snuggled up in his arms.

“Well, young fellow,” said the eager boy, “if I ever get back to Bayport once more, you’ll come with me.”

“Its owner may have something to say about that,” Frank observed.

Just then a shadow crossed the entrance to the cave. The boys looked up to see a girl peering in at them. She was a dark-skinned, gypsy-like young creature with big eyes.

“Pepita!” she cried when she saw the dog. “Pepita!”

“Your dog?” asked Joe, disappointed.

The girl nodded. The guard looked on with interest.

As the young woman came closer Frank and Joe noted something that horrified them. In the center of the girl’s forehead, plainly visible, was an ugly mark.

It was a brand—the symbol P which they had seen before—burned into her flesh!

The Mexican maid was trying as best she could to coax the pup to come to her, but the independent little animal seemed to prefer to stay with its new friends.

“Look here,” cried Frank. “How did you get that mark on your forehead?”

The girl was puzzled. She did not understand. Frank leaned forward and lightly touched the branded symbol. A look of terror crossed her face. She glanced over her shoulder as if fearful of being overheard.

“Eet was Pedro,” she whispered.

“He branded you!” Joe exclaimed in horror.

Although she did not understand his words she gathered their meaning. The girl nodded slowly.

“Pedro—not please wit’ me,” she answered.

Then she shrugged and gestured toward the mark again.

“He branded you because he was angry with you?” Joe asked.

The girl nodded her head vigorously. Then she called to the dog again, trying to coax it away from the boys.

“So that’s the sort of fellow Pedro Vincenzo is,” muttered Frank indignantly.

The boys knew then that Pedro’s promise to brand them if Tremmer did not keep his bargain was no empty threat.

By signs with his hands Joe tried to make the girl understand that he would like to keep the dog.

“I’ll buy him from you,” he said. Then his face fell. “I forgot. The bandits took all our money.”

The girl spoke sharply to the dog in Spanish. The animal reluctantly moved toward her. Joe suddenly thought of the strange bracelet he had discovered on the floor of the other cave. He took it from his pocket and held it out to the girl, at the same time pointing at the dog.

The girl exclaimed with delight when she saw the piece of jewelry. She reached for it shyly, slipped it over her arm, and gazed at it with shining eyes. Again Joe pointed to the dog, making signs to indicate that he wished to make an exchange.

The girl understood. She did not try to coax the animal to come to her any more. Admiring the bracelet, she withdrew from the cave and slipped away.

“Come back, pup,” said Joe to the dog. “You belong to us now.”

The animal was quite willing. He seemed to understand and frisked about the boys, barking happily as if to show his appreciation.

“All we have to worry about now,” Frank remarked, “is how we are going to get him back to Bayport.”

Even the antics of the dog, however, could not relieve the suspense they were enduring. If their father should not appear in the camp by the end of the hour, Vincenzo would certainly wreak vengeance upon them. And if he did appear, what then? Fenton Hardy would be unable to aid them, and the torture of the Fire Ceremony might be carried out just the same.

Frank looked at his wrist watch.

“Fifteen minutes,” he said quietly.

The brand they had seen on the girl’s forehead told them that they could expect no mercy from their captor. Pedro Vincenzo was cruel and relentless. He would carry out his threat.

Frank got up and went over to the mouth of the cave. Some of the natives were coming back from the other side of the river, and as they arrived he could hear Vincenzo arguing with them.

Suddenly a great shout went up.

One of the tribesmen ran up to Vincenzo and grasped him by the arm, at the same time pointing to the wall of the cañon that rose high from the opposite bank of the stream. Frank gasped.

At the top of a narrow trail, meandering up the side of the wall, he saw three figures. Two of them were natives. The other one was a white man!

Was the latter Fenton Hardy?

Frank could not distinguish the form very plainly at that distance.

“Joe!” he called. “Come here, quick!”

Joe leaped up and ran to his brother’s side, the dog leaping gaily at his heels.

Vincenzo and the natives were silent. They were watching the three figures beginning the difficult descent down the steep wall of the cañon.

“It’s Dad!” exclaimed Joe.

“I’m not sure yet. Perhaps it’s Tremmer coming back.”

“No, he isn’t dressed like Tremmer.”

Suspense gripped the lads as they watched the three men slowly making their way down a trail. Even when the trio finally reached the base of the cliff, the boys were unable to learn for certain if the newcomer was really Fenton Hardy.

The three men got into one of the dugout canoes and began to paddle across the stream. From the actions of the deserters, who immediately made preparations to return, the boys were convinced now that Tremmer had somehow kept his promise.

At last the canoe reached shore, and one of the natives leaped out. He was followed by a white man. Joe and Frank uttered a simultaneous groan of despair.

“Dad, oh, Dad!”

It was indeed Fenton Hardy!

How had Tremmer learned of the detective’s whereabouts? How had he lured Mr. Hardy so easily into Pedro Vincenzo’s trap?

As the boys watched closely, they could see Pedro step forward. He gave a curt order to the natives at his side.

Instantly those strong men flung themselves on the detective and pinioned his arms behind his back.

Fenton Hardy was now a prisoner, as well as his sons!

Fenton Hardy was the sort of man who could accept apparent defeat with a smile. When he was brought to the cave where his sons were imprisoned, he wasted no time bemoaning his luck. He greeted the boys warmly.

“We don’t seem to be having much success in Mexico,” he said. “I thought I was walking into a trap when those natives told me I would find you here, but I had to come.”

Pedro Vincenzo, who had come up the trail behind the men guarding Fenton Hardy, laughed triumphantly.

“You bit off more than you could chew when you thought you could beat me,” he said. “You may be a smart man in the States, Hardy, but you’re mighty small down here.”

“I’m not through yet,” replied Fenton Hardy significantly.

“You’re through, all right, but you don’t know it. You and your boys.” Vincenzo put his hands on his hips and showed his teeth in a wicked grin. “I’m sorry to see Tremmer get away from me——”

“Tremmer!” exclaimed Mr. Hardy in surprise.

“Yes, Tremmer,” snarled Vincenzo. “The man you wanted to complete the case against the Rio Oil people. You didn’t know I had him here, eh? Well, you won’t take him back with you to give evidence.”

Fenton Hardy glanced at his sons.

“Is this true?” he asked quietly. “Was Tremmer in this place?”

“Yes,” replied Frank. “He escaped an hour ago.”

“Two natives came to my camp beyond the gorge and told me they could show me where my sons were held captive,” explained Mr. Hardy. “I came with them—and here I am. I suppose that was Tremmer’s work.”

So Pedro had not known of the whereabouts of the boys’ father!

“We made a little deal,” said Vincenzo. “He said he would see that you came here if I let him go. I didn’t believe him. Even yet I cannot figure how he knew you were nearby. But he kept his word and I’ll keep mine. I’ve frightened that fool so that he’ll never set foot on American soil again.”

Frank and Joe said nothing. Their best chance of escape, they were aware, lay in making Pedro believe that they were submissive. Fenton Hardy evidently had the same thought in his mind, for he said:

“All right, Vincenzo. You win. You’re too smart for us. What do you intend to do with us now?”

“That remains to be seen,” replied the outlaw. “Now that the natives have come back to me they feel I ought to give them a little entertainment. Perhaps the Ceremony of the Fire will please.” He laughed maliciously. “The three of you will look handsome returning to Bayport branded on your foreheads—a little souvenir of your visit to Mexico.”

He strode away, chuckling to himself.

“It’s all our fault, Dad,” said Frank ruefully. “We got you into this jam.”

“But you found Tremmer,” said Mr. Hardy. “Tell me about it. Perhaps we haven’t lost the fellow after all.”

“If we can ever get in touch with Yaqui we’ll find him fast enough,” Joe said.

The boys related their story: how they had started out into the desert and had followed the trail of the caravan, only to be captured by the bandits and turned over to Pedro Vincenzo; how they had discovered Tremmer, and of the conversation they had had with the fugitive bookkeeper. They explained how the missing witness had led the revolt, and then escaped.

“What have you been doing, Dad?” asked Joe when the recital was finished. “How did you get into this part of the country?”

“When I left you,” Fenton Hardy explained, “I was on the track of certain people who could give me information about the oil frauds. I rounded up half a dozen of the men involved in the case and turned them over to the authorities. But I found that the only evidence that would clinch the case would be that of Elmer Tremmer—if he could be found.”

“How did you discover that we had been captured by Vincenzo?” asked Frank.

“I didn’t know that. But I learned that you had been seen on the edge of the desert,” explained Mr. Hardy, “and I followed the trail from that point. Later I was told by a native that two American boys had been seen in a camp near the river, so I came in this direction. A half-breed came to my camp two nights ago and went away in a hurry. I imagine he must have been one of Pedro Vincenzo’s spies. But instead of telling Vincenzo he went to Tremmer.”

“That explains why Tremmer became so courageous all of a sudden,” remarked Joe. “He knew he could bargain with Pedro.”

“We must figure out a way of escape,” said Mr. Hardy. “We’re not beaten as long as Yaqui can keep on the trail of the missing witness.”

“I told him to blaze the trees as he went,” said Joe. “If we can get out of here we should be able to follow him easily enough.”

“Well,” volunteered Frank, “Yaqui told me where he had hidden the horses he brought back with him. He said there is a ford across the river a little farther up. If I can get out of here tonight I’ll find the horses and perhaps we can make our way across the river.”

Fenton Hardy gestured toward the guard who was standing at the cave mouth.

“He will be the chief obstacle.”

“We’ll have to wait until it gets dark,” said Joe in a low voice.

The three were very hungry. As the boys shared with their father the food Yaqui had left, they told Fenton Hardy how Vincenzo had adopted a starvation policy toward them.

The day passed slowly. They wondered if Pedro Vincenzo planned to hold the Ceremonial of the Fire that night. But darkness fell, and their captor did not come near them.

“I’m going to try to slip out tonight,” said Frank. “When I find the horses I’ll bring them as close to the camp as I dare. Then, if you can get past the guard, come on out and join me.”

“How shall we know when you’re ready?” Joe asked.

“I’ll imitate a wildcat’s scream.”

“You aren’t out of the cave yet,” Fenton Hardy reminded him. “That comes first.”

“I’ll get out somehow.”

“Dad, in the excitement we forgot to tell you something we discovered,” said Joe suddenly.

“Sure thing,” echoed his brother. “We’ve found out an important secret.”

“I’m interested,” answered Mr. Hardy. “What is it?”

“Well, we were able to track Pedro to a certain cave and located a box he had secreted.”

“It was wrapped in a Bayport newspaper!” interrupted Frank.

Mr. Hardy smiled. “Sounds as if the contents of the cache came from our own home town.”

“I’m sure they did,” explained Frank. “There were thousands of dollars rolled up, Pedro’s share in the illegal stock sale.”

“Maybe more than his share,” was Mr. Hardy’s comment. “The man isn’t above robbing his friends. I know that from information I have uncovered lately.”

After this conversation there was silence for a while.

“I do wish they would bring us a drink of water,” said Mr. Hardy presently.

Thereupon the detective got up and went to the mouth of the cave. As he understood Spanish, he was able to talk to the guard. Sternly he demanded food and drink. After a brief argument the sentry went on up to the main camp. Another native quickly took his place, however, just as Frank was beginning to think this would be an excellent time in which to slip away.

In a little while the first guard returned. Greatly to the surprise of the boys, he carried with him an earthen plate of food and a gourd of water.

He spoke to Mr. Hardy in Spanish and offered him the food.

“Don’t drink the water!” whispered Frank tensely.

“Why not?” demanded Joe in surprise. “I’m dying of thirst.”

“Don’t drink it!”

Joe and Mr. Hardy were puzzled by Frank’s insistence. They ate the food, however, but thrust the water aside.

The sentry was astonished. He pointed to the gourd.

“I’m suspicious of it,” Frank said quietly. “Let the guard drink it if he wishes.”

Mr. Hardy indicated that the man himself might have the water. The sentinel thereupon picked up the gourd and drank deeply, smacking his lips in appreciation. He went out of the cave and sat down near the entrance. Then he spoke to his companion guard, who went away.

“How do you think you are going to get out of here, Frank?” asked his father.

“Wait and see.”

The sentry took another drink. Then the Hardys noted that the man appeared to grow drowsy. His head sank slowly upon his chest. After a little while he revived momentarily and again quaffed deeply from the gourd, only to grow sleepy almost immediately.

“I suspected there was dope in that gourd,” Frank whispered.

As he spoke, the guard suddenly slumped forward. The gourd tumbled from his hands into the dust. The man fell over and sprawled unconscious in front of the cave.

“You were right, Frank,” said Joe excitedly. “And that stuff was meant for us.”

Frank crept to the opening and looked out.

“How did you know the water was drugged?” Joe asked.

“Yaqui warned me to expect something like that. He overheard the two guards talking last night. One of them said we were to be given a drink made out of a narcotic variety of cactus.”

The unconscious man lying at the entrance evidently had not been told of the plan. He was snoring heavily.

“Why can’t we all escape now?” said Joe.

“We won’t get very far without horses,” Frank reminded him. “If we are missed before we have time to get the animals we’ll be captured and brought back in a hurry. If you and Dad stay here no one will become suspicious, should any of Vincenzo’s men accidentally come up here. You will cover my escape.”

“Are you sure you can find the horses?” asked Fenton Hardy.

“If they haven’t run away. I ought to be back in less than half an hour.”

Frank slipped out into the night. Fenton Hardy and Joe settled down to wait for him.

As he listened for Frank’s signal, Joe told his father a more complete story of the adventures he and his brother had undergone from the time their father had left them at the Marcheta villa.

“Tremmer always was a weak sort of character,” Mr. Hardy said, after Joe had related how the fugitive bookkeeper had refused to help them. “He isn’t crooked, though. I think Vincenzo has frightened him so thoroughly that he is desperate. The oil company faker has persuaded him that we want to arrest him and that he’ll be sent to the penitentiary if he goes back to the States. It’s too bad he has slipped through our fingers. I think I might have been able to have made him listen to reason.”

“We haven’t lost him yet. Yaqui is on his trail.”

“Now our problem is to follow the Indian,” smiled Fenton Hardy.

“We may not be able to do much until daylight. Yaqui said he would blaze a trail on the trees as he went.”

Mr. Hardy took a powerful electric flashlight from his pocket.

“Perhaps this will help,” he said.

“It will be the very thing!” Joe exclaimed. “I hope Frank finds those horses. With any luck at all, we ought to be able to overtake Mr. Elmer Tremmer before he gets very far away.”

The minutes went by. Joe began to grow nervous.

“I hope nothing has happened to Frank,” he said.

“I’m not worrying about him,” Fenton Hardy said confidently. “You boys always seem to land on your feet.”

“We landed in a tight fix this time,” Joe answered.

Suddenly, away up in the darkness of the gorge, they heard a harsh, savage screech. It was exactly like the scream of a wildcat. Joe and his father leaped to their feet.

“Frank’s signal!” exclaimed the latter. “I knew he wouldn’t fail us.”

They went out of the cave. The snoring guard did not stir. Up near the native camp they saw a fire, while dark figures moved back and forth against the ruddy glare.

“The coast is clear,” whispered Joe.

Quickly they flitted through the gloom until they reached the trail. They encountered no one, and the sullen roar of the river drowned any sound they might have made.

Joe had not forgotten their little pet, which was close at his heels.

The boy and his father rounded a bend in the trail and left the camp behind. After five minutes of brisk walking they saw the shadowy outline of horses ahead of them. They heard a low whistle.

“We’re here, Frank!” called out Joe softly.

Frank had succeeded in locating the ponies, which were spirited animals. They were saddled and bridled. Everything was in readiness.

“I’ve been looking around,” said Frank. “There’s a path leading down to the river from this place and the water seems shallow. It’s a ford, I’m sure. I think we can get across to the other side. Then we’ll work our way along the bank and try to pick up Yaqui’s trail.”

“Dad has a flashlight,” Joe told him.

“Good work. We won’t be able to use it while we’re in sight of the camp, but it will be handy later on.”

The three Hardys mounted their ponies and rode down the path to the stream, where the animals plunged into the water without hesitation. The river was shallow and the current was not swift. They made the crossing without difficulty. As if by instinct the lead pony found the trail on the opposite bank.

When the Hardys came in sight of the camp again they proceeded cautiously lest they be seen by someone on the opposite shore. Most of the natives were asleep. The others were so busy with their own concerns, that by the time the trio reached the place where they had last seen Elmer Tremmer they were confident they had not been observed.

Before them, visible in the moonlight, a winding trail led up the wall of the cañon. The ponies followed it without hesitation. The sure-footed animals took to the narrow path as if it had been a highway.

“I’d think twice before I would tackle this without a horse,” murmured Joe as they made their way on up the steep face of the cliff. “One false step, and a fellow wouldn’t stop rolling until he hit the water.”

“These ponies don’t make false steps,” Frank assured him.

They finally reached the top of the cañon wall. Glancing back, they could see the white gleam of the river far below in the moonlight, and the red glare of the natives’ campfire in the distance. Before them loomed the dark wall of a forest.

“Now, if Yaqui has kept his promise and blazed the trail for us we’ll set out after Elmer Tremmer,” declared Frank. “I guess it’s safe to use the flashlight now, Dad.”

Fenton Hardy snapped on the light. The brilliant beam shone on the tangle of tropical vegetation before them. It picked out a patch of white on a tree trunk where the bark had been slashed off with a sharp knife.

“Good old Yaqui!” exclaimed Joe. “It’s as plain as a Bayport street sign.”

The Hardys rode toward the blazed tree. The flashlight showed them a fresh trail leading into the bush. A few yards ahead they saw a second blaze. Fenton Hardy led the way with the light, and they all plunged into the forest.

Thanks to Yaqui’s signs they were able to follow the bush trail without difficulty, although their progress was slow. They had the satisfaction of knowing that they were steadily leaving Pedro Vincenzo and his men behind, and at last were drawing closer to the fugitive witness whose trail had brought them from far-off Bayport into a wild region of Mexico.

The bush thinned out eventually and they reached a clearing. In the middle of this open space towered an enormous tree.

“Look!” cried Joe excitedly. “The mark of the P!”

His sharp eyes had caught sight of a sign branded into the bark of the tree. Mr. Hardy turned the flashlight directly upon it, and they saw again the familiar symbol of the initial in the fagot fire.

“Pedro Vincenzo puts that symbol of his in strange places,” remarked Fenton Hardy, examining it curiously. “I wonder why he went to all the trouble of leaving it here.”

“It’s probably there as a sign in case any of the natives should get lost trying to find their way back to the cañon,” Frank ventured. “Anyway, we haven’t time to bother about it now. I see a fresh blaze on the other side of the clearing.”

They struck again into the forest, leaving the mysteriously branded tree behind. Yaqui had been thorough about his work, and the Hardys followed the trail from blaze to blaze. In about an hour’s time they came to the edge of the forest and emerged onto a hillside covered with low brush. At the foot of the slope was a rolling meadow, while a mile away they could see a glimmer of light.

“Perhaps Tremmer decided to camp for the night,” Joe suggested.

“Let’s hope so,” replied Frank.

Out in the open they traveled at a faster pace. Soon they reached the foot of the slope and struck out across the level country. As they rode as fast as they could in the direction of the light, they saw the dim outline of a hut.

“It may be only a herder’s cabin,” said Fenton Hardy.

“If it is we’ve run into hard luck,” Frank remarked. “There aren’t any more trees to follow. We may lose the trail entirely.”

Impatiently they rode toward the tiny cabin. As they drew up in front of the door a figure emerged. The flashlight shone upon the familiar face of Yaqui.

Frank and Joe uttered cries of delight as they flung themselves out of their saddles.

“Yaqui!” cried Frank. “We followed your trail. Is Tremmer far ahead?”

The Indian smiled. Then he gestured toward the hut.

“This is the end of the trail,” he told them. “The white man is inside.”

“Tremmer is here?” questioned Fenton Hardy.

The Hardy boys found Elmer Tremmer, the fugitive bookkeeper, lying on a straw pallet on the floor of the gloomy little hut. He was in a state of utter collapse.

“I give up!” he cried weakly, as they entered the building. In the gleam of the flashlight his face was pale and worn. “I’m ready to go back. No matter what it costs—even if I go to prison—I’ll go back.”

The strain of that long journey through the bush had told heavily on him. He was not a strong man, and now he was physically exhausted.

Fenton Hardy sat down beside him.

“You’ve been very foolish, Tremmer,” he said. “Why did you run away?”

“Because Vincenzo warned me. He said the authorities would arrest me for my part in the Rio Oil affair. But it wasn’t my fault, Mr. Hardy. I swear it. I kept the books, but I didn’t know the business was crooked. I see it now, of course—but it’s too late.”

“It isn’t too late. Don’t you realize that Vincenzo merely wanted you out of the way so you couldn’t give evidence against his associates?”

“Your sons told me that. But I didn’t believe them. I thought it was a trick to get me back to the States.”

“It wasn’t a trick. I’m authorized to promise you, Tremmer, that no action will be taken against you if you will come back to Bayport and give your evidence for the State.”

“I can really go back? And I won’t be put in prison?” cried Tremmer eagerly.

“You have my promise,” said Fenton Hardy firmly.

“Then,” returned Tremmer, “I’ll return with you. And believe me, I’ll be glad to see Bayport again. Mexico is a wonderful country, but it’s no fun being a prisoner and thinking you’re a fugitive from justice at the same time.”

Frank and Joe were hilarious with joy. Their mission to Mexico had been successful at last. They clapped Yaqui on the back and assured him that he deserved most of the credit. Even the dog, Egg, seemed to realize that the occasion called for a demonstration, and he went scampering about the hut barking with delight.

“I must tell you,” said Elmer Tremmer, “that Vincenzo has other plans up his sleeve. I overheard him talking to one of his men yesterday. He is planning to kidnap a girl—her name is Dolores——”

“Dolores Marcheta!” cried Fenton Hardy.

“Yes. That’s the name,” exclaimed Tremmer. “If you know the family, they must be warned.”

“Then there is no time to lose,” declared Frank. “The Marchetas are friends of ours. Before we leave Mexico we must see that Pedro Vincenzo is put behind the bars where he belongs.”

The Hardys and Mr. Tremmer set out early the next morning, and with the guidance of Yaqui soon found their way to the main highway. They came to a large inn where they were able to hire an automobile that whirled them over the last thirty miles of their journey in less than an hour’s time. It was midafternoon when they reached the home of Señor Marcheta.

Fenton Hardy and his sons received a royal welcome. Señor Marcheta and Juan made no secret of the sense of relief they felt in seeing their American friends again.

“We were sure you must have been captured by bandits when the soldiers we sent failed to find you,” declared Juan. “We were going to organize a search party.”

“We were,” laughed Frank. “And the search party will still be useful.”

They told the story of their adventures. When Señor Marcheta learned that Vincenzo was still planning villainy against his household he lost no time getting into action.

“We’ll settle that fellow without any more delay,” he said. “Now that we know where to find Vincenzo’s headquarters, we can organize a raiding party.” Then, turning to the detective and his sons, Señor Marcheta said, “No doubt, after your trying experiences, you will prefer to rest. If you will permit us to have the services of your Yaqui as a guide——”

“Don’t you want us to come along?” cried Joe. “Do you think we’ll let the Indian have all the fun? Just try to keep us out of this excursion.”

Señor Marcheta laughed.

“My little joke,” he apologized. “I might have known you would insist upon being present at the end.”

Accompanied by a squad of a dozen soldiers, Señor Marcheta, Juan, Yaqui, Fenton Hardy and his sons set out early the following morning for the cañon. Swift automobiles brought them within a few miles of their destination. Then they mounted ponies and rode down a side trail toward the river. When the soldiers came in sight of the native village they swooped upon it, hoping to capture Pedro Vincenzo by surprise.

The wily rogue was not to be caught napping, however. He had evidently suspected the truth when he had learned of his prisoners’ escape. Greatly to the disappointment of the raiding party the village was deserted. Not a native remained. Pedro Vincenzo and his followers had taken to their heels.

The soldiers scouted around for some time hoping to pick up the trail, but without success. Señor Marcheta was crestfallen.

“As long as that rascal is at large,” he said, “I shall never feel that any member of my family is safe.”

Joe was looking thoughtfully across the river.

“Frank,” he said, “I have an idea. Let’s take Yaqui and a couple of the soldiers. I may be all wrong, but I think I can find Vincenzo’s hiding place.”

Frank was puzzled.

“What’s the idea?” he asked.

“The mark on the door,” Joe replied mysteriously.

Yaqui and two of the soldiers readily agreed to follow him. Juan and his father begged to be allowed to come also. Joe led the party across the river and up the path to the top of the cañon wall, then through the bush, following the trail blazed by the Yaqui in the pursuit of Elmer Tremmer. At last they came to the huge tree in the clearing.

“It’s just a hunch,” said Joe, pointing to the familiar brand in the surface of the tree, “but Vincenzo had a habit of putting that mark on doors.”

Frank quickly seized his brother’s idea. The Hardy boys dismounted hastily and went over to the tree. After a brief examination they shouted with triumph, and called to the soldiers. Joe seized a knot in the rough surface, tugged at it—and the whole side of the trunk came away.

There was revealed a cunningly contrived door. The Hardys climbed through the opening, and looked down an aperture. They saw a flight of steps leading below the ground, and quickly descended. A moment later those above heard shouts and cries for mercy. Then, at the foot of the stairs, appeared Joe and Frank dragging a craven figure.

The man was Pedro Vincenzo. The mark on the door had revealed the secret of his last hiding place.

Señor Marcheta and Juan stared at the prisoner.

“Why, it’s Pedro Pancho!” cried Juan.

The captive glared at Señor Marcheta.

“I see the game is up,” he said bitterly. “But if it hadn’t been for those American boys, I’d have had my revenge on you, Marcheta.”

“Thanks to the Hardys,” replied the Mexican gentleman with dignity, “my family will now know peace and security. As for your fancied revenge, you are aware that I never harmed you. It was all in your evil imagination.”

He spoke curtly to the soldiers and turned away. In a moment Pedro’s arms were bound tightly behind his back. He was mounted upon a pony and thus brought ingloriously back to the camp.

So the mission of the Hardy boys to Mexico was finally crowned with success. Pedro Vincenzo, in captivity, proved to be a frightened coward. When he learned that Tremmer was no longer afraid of him and that the former bookkeeper had promised to give evidence for the State, he talked freely and exposed all the crooked dealings of his associates in the Rio Oil Company. In so doing he hoped to win favor, but it gained him little. For the abduction of Juan and for many other crimes which were traced to him by the Mexican authorities he was sentenced to a long term in prison.

As for Elmer Tremmer, he returned to Bayport with Mr. Hardy and the boys—to say nothing of the dog Egg—and went on the witness stand to clinch the State’s case against the crooked promoters. The authorities succeeded in rounding up every member of the fake oil company.

Joe and Frank received high praise for having located the box in the cave, where Vincenzo had stored much of the loot from the sale of the bogus stock.

The shareholders who had been victimized by the promoters were reimbursed. Fenton Hardy, for his work in running down the missing witness, was paid a handsome fee.

“But I don’t deserve it, as a matter of fact,” he told the shareholders who had employed him. “My sons really should have the credit.”

Although Frank and Joe insisted that they were “just trying to help,” Fenton Hardy shared the fee with them. He put the money to their credit in the bank where they already had a substantial sum on deposit in the form of rewards paid them for their work in solving other mysteries.

“We didn’t do it for money,” said Frank. “We had a million dollars’ worth of adventure out of it.”

“And we brought back a dog for Mrs. Smith,” Joe reminded him. “I hate to part with the little animal. But after all, the landlady gave us some mighty valuable clues. We first saw Pedro’s mark on the door in her house.”

“By the way,” remarked Fenton Hardy, “I think you told me Vincenzo had damaged your motorboat. Did you have it repaired?”

“Yes. The boat is all right now,” said Frank.

“How much did it cost?”

“Fourteen dollars and fifty cents.”

Fenton Hardy counted out the money and put it on the desk.

“When I told the shareholders the whole story,” he said, “they particularly requested that you be paid for the damage to the boat.”

“We shouldn’t take that money,” remarked Frank.

“Why?” asked Fenton Hardy.

“Because,” returned Frank wisely, “if Pedro hadn’t bumped into us we probably shouldn’t have located the missing witness or solved the mystery of the mark on the door.”

THE END

TRANSCRIBER NOTES

Misspelled words and printer errors have been corrected. Where multiple spellings occur, majority use has been employed.

Punctuation has been maintained except where obvious printer errors occur.

[The end of The Mark on the Door by Franklin W. Dixon (Stratemeyer pseudonym).]