“THE Sahara Desert! Adventure! Exploration!” breathed Joe Lewis, as he sat with four companions on the deck of the steamer Sylvania, awaiting their first glimpse of North Africa.

“It’ll be wonderful!” muttered Bob Holton, who was also deeply touched. He, like his chum, had often pictured this mission into the heart of the vast expanse of sand. Soon it would be the real thing. Already the youth could feel his feet plod through the loose soil, could sense the delight of long traveling in a little-known land.

Dr. Kirshner, a noted archæologist, looked up from the book he was reading. His bronzed face took on a wide smile as he scrutinized the two young men.

“Got the old spirit, all right,” he said with twinkling eyes. “I suppose it came from that expedition in Brazil. Every explorer gets it sooner or later.”

“That’s right,” agreed Mr. Lewis, Joe’s father. “They say the main characteristic of a true explorer is his ability to sense the thrill of adventure.”

“Then we’re real explorers. Isn’t that right, Dad?” grinned Bob.

“‘We’?” asked Mr. Holton, trying to appear serious. “Where do you get that ‘we’ stuff? You and Joe have only bothered us on one expedition. We men have faced the scorching sun scores of times, and should by now have caught the true meaning of it all. But you boys – ”

“Wait a minute,” cut in Bob, determined not to be beaten so easily. “Where would you have been if it hadn’t been for Joe and me? It was our ingenuity that brought about the success of the expedition.”

“Well, I must say I hadn’t thought of that before,” laughed Mr. Holton.

“It’s true, all right.” Bob stoutly defended himself and his chum. “If you say the word I’ll prove it.”

Mr. Holton smiled. He took a great delight in arguing in a friendly manner with his son, although at times he was forced to admit defeat. This time he was satisfied to drop the matter and turn his eyes to the western sky, where the sun, a great ball of red fire, was sliding into the bluish waters of the Mediterranean. Gradually the ball faded from view, leaving a soft blue sky, which a moment later became streaked with long gold streamers. At last these became molded into one great mass of color and light, crossed and dotted with every hue of the rainbow. Slowly the spectacle faded from view, and the sky became a warm blue, out of which came countless glittering stars.

It was a wonderful sight, and although the adventurers had witnessed it several times before, they never seemed to tire of it. Bob and Joe especially were deeply stirred.

“Now that we’ve seen our last sunset on this voyage, suppose we get our belongings together,” said Mr. Holton, getting up from his chair. “It won’t be long until we reach Algiers.”

“And if what we’ve heard is true, it’s a wonderful city,” added Mr. Lewis. “Has the most unusual blend of things Arab and European on the globe. Monuments, mosques, palaces, everything and more that characterizes the spirit of North Africa.”

He arose and led the way up the deck to the cabin, where already people were gathering to await the first sight of land. Among the passengers were brightly garbed Egyptians, Algerians, Arabs, and many others with quaint and picturesque costumes. Everyone was in a gay mood, laughing and talking merrily. That is, all but two tall Arabs, whose quiet gaze was fixed on Bob, Joe, and the others of the American expedition. That the men intended mischief was sensed by the boys, although their elders had caught no element of danger.

“Wonder what they want?” murmured Bob, in an undertone to his chum. “Fact is, I’ve noticed them before, but never said anything about it. They seem to follow us, for some reason or other.”

Joe nodded.

“I’ve thought the same thing,” he said quietly. “But as they made no move against us, I almost forgot about it till now.”

The youths said no more until they reached their stateroom, which was directly across the hall from that of their elders. As soon as their belongings were together, Bob decided to mention the matter to his father and friends.

“Ten to one they haven’t noticed these men,” he said to Joe, “and it might be best for us to put ’em wise.”

The youths found their companions preparing to leave for the deck and motioned for them to come in the room. Then Bob told of the actions of the two Arabs, pointing out that they probably had no good intentions.

The men listened closely, eager to get all the details. When the boys were finished, Mr. Lewis looked grave.

“They probably heard Dr. Kirshner mention the hidden treasure,” he said soberly, at the same time glancing about as if he expected to see the Arabs at the door.

“Hidden treasure? What treasure?” demanded Joe excitedly, while Bob looked up in surprise.

“It may only be a yarn,” replied Dr. Kirshner. “In fact I just heard about it this morning. An intelligent Arab with whom I made friends pointed out that he had definite information that there were great riches amassed in a cave in the heart of the Sahara Desert. It seems that they had been placed there by native tribesmen, or Tuaregs, who inhabited this region hundreds of years ago. Tuaregs even today are very fond of raiding caravans and small towns. Got it in their blood, I guess.” He paused a moment for breath, and Bob seized upon the opportunity.

“But why did the Arab tell you this?” he asked. “Didn’t he know – ”

“I know what you’re thinking,” the scientist interrupted. “You’re wondering why I got in on this. I did too at the start. But as soon as he had finished with the details, he told me that he was not equal to making the expedition alone and had no relatives or good friends to accompany him. He went on to say that few expeditions are sent out into those remote regions, and that he would gladly share the treasure with us if we would go with him.

“Now as this treasure cave is supposedly in the region that we intended to explore, your dads and I could see no reason for not taking him up. His services as a guide will also be invaluable.”

“But – but how does he know where to search?” questioned Joe Lewis, his tone indicating that he was greatly puzzled.

“He has a map,” returned the archæologist. “Got it from an old tribesman who was about to die. Whether or not it is accurate, we have yet to see – if nothing prevents us,” he added significantly.

“Nothing will – if we can help it,” said Bob, delighted at such an opportunity.

A few minutes later they lugged their possessions out on deck. And they were none too soon, for it was scarcely ten minutes later that the lights of land became visible – dimly, of course, but they were there.

“At last,” sighed Mr. Holton, who, although he enjoyed the long voyage, was anxious to reach his destination.

Although land was a great distance away, the adventurers went to the prow to catch a first glimpse of that mysterious country on which they would soon set foot.

Bob and Joe watched closely as the myriad of lights grew more plain. A stronger beam flashed from the Cape Matifou lighthouse, and numerous lights from ships in and about the harbor were also visible. No more could be seen. But it was enough. Bob and Joe were convinced that Algiers was a charming city indeed.

“How large a place is it?” asked Joe, as the Sylvania neared the port.

“About two hundred and fifty thousand,” returned Mr. Holton. “And all different races, from Americans to Turks and Jews. Oh, we’ll see sights all right.”

Gradually the boat pulled into the harbor, reversed her engines, and stopped at a large dock. Then among lights the gangplank was lowered, and the boys and their elders soon found themselves among the many hurrying passengers. Lights were everywhere, almost as numerous as in an American city, and they had no trouble in finding their way to a hotel.

“Oh, by the way,” exclaimed Joe with a sudden recollection, “what became of your friend the Arab – the one who knows about the hidden treasure?”

“He’s at another hotel,” replied Dr. Kirshner. “I have his address on paper. We’ll go over there in the morning. He had already made reservations at this hostelry or would have put up with us.”

The remainder of that evening was spent quietly, for the explorers were tired after the long journey on the Sylvania.

Bob and Joe were up early the next morning, and after a small but satisfying breakfast they started out for a short walk. But they had scarcely covered a square when Joe, who had happened to glance back, stopped suddenly and nudged his friend.

Bob looked, and an answering expression of surprise and anger came on his face.

Walking slowly into the hotel were the two Arabs who had acted so suspiciously on the ship.

CHAPTER II
Scoundrels at Work

“WHAT do you suppose they want?” asked Joe, as the youths followed the movements of the Arabs.

“They’re not there for any good,” returned Bob, a look of anger, and at the same time anxiety, on his face. “Probably want to find that map that tells of the hidden treasure. Oh, of course it could be a coincidence that they picked the same hotel that we did, but it isn’t likely.”

The boys watched the suspicious characters until they disappeared into the hotel. Then Joe suggested that they cautiously follow.

“All right,” Bob agreed. “But we must be careful and not get too close. They might have guns and think nothing of using them, and they could probably get away in this country.”

Slowly the youths moved up to the entrance and peeped around the corner. Satisfied that there was no one in sight, they went inside.

“Nobody here but our dads and Dr. Kirshner,” observed Bob, glancing about. “I wonder if they noticed the Arabs?”

“Let’s ask them.”

The men had noticed the fellows, they said, but thought nothing about it. Why? Was anything wrong?

Bob explained that they were the two who had acted in a suspicious manner on the ship, and at once the scientists’ faces lightened.

“Come on,” urged Dr. Kirshner. “We can’t get there any too rapidly. When they find that we haven’t got the map, they’ll probably help themselves to money and anything else that happens to be lying about. They may even search other rooms.”

Hastily, and yet quietly, the boys and their elders went up the stairway. They were unarmed, their revolvers and other firearms having been left in their rooms. This might prove a handicap if the Arabs possessed weapons, but the Americans thought nothing of the risk they were taking.

“We’re five to two, even if we haven’t our guns,” said Bob, clinching his fists. “They’re likely to be shaken by numbers.”

But Dr. Kirshner, who knew the ways of these cunning natives, smiled grimly.

In a short time they reached the floor on which were their rooms and turned cautiously down the hall. With utmost care lest they be discovered, the explorers tiptoed up to their rooms.

Mr. Holton took the lead and glanced around the door into the room. A moment later his face scowled.

“What is it?” demanded Joe, in a whisper. “Are they inside?”

Mr. Holton shook his head.

“Worse than that,” he said solemnly. “Take a look.”

While the others are taking in the situation, it might be well to tell something about Bob Holton and Joe Lewis and, incidentally, their fathers.

Bob was a big, well-built youth of some eighteen years. He was particularly fond of adventure and life in the open, and always welcomed an opportunity that might bring about a realization of his desire.

Joe, who was about the same age, was of medium size and strength, with a naturally dark complexion that was now still further darkened by the tropical sun. He, like his friend, was fond of adventure, hunting and fishing and hiking whenever the opportunity presented itself.

The youths were together much of their time and agreed on practically every point. Their home was in Washington, D. C., where their fathers, Mr. Holton and Mr. Lewis, were employed as naturalists by a large museum.

A short time before, the youths were successful in persuading their fathers to take them on an expedition to unexplored Brazil. Here they helped the naturalists shoot and classify wild animals, birds, and reptiles and had many thrilling adventures with wild animals and savage Indians. How they fought hand-to-hand with a huge jaguar, barely prevented themselves from being crushed by a terrible anaconda, battled against rapids, and finally became lost and wandered for days in the world’s greatest jungle are told in the first volume of this series, entitled, Lost in the Wilds of Brazil.

The boys spent the following winter finishing up in high school, and scarcely was graduation over when their fathers were requested by the museum to make an expedition to the Sahara Desert to collect specimens of any animal life that might be present in the remote interior. Dr. Kirshner, of whom something has been said, wished to accompany the naturalists to investigate the remains of ancient civilizations. At once Bob and Joe requested that they be taken also, and after careful consideration their elders at last consented. What the boys were particularly looking forward to was taking motion pictures of the desert, for they had been engaged by the Neuman Film Corporation to get many unusual scenes.

Less than a week later the expedition sailed on the steamer Sylvania and made the long voyage without any special incident.

Now let us return to the boys, as they advanced into their elders’ room.

At once their mood changed, an expression of astonishment, later turning to anger, creeping over their faces.

Everything in the room was in the wildest disorder. Clothes, shoes, satchels, rifles, papers lay scattered about, the scene suggesting that a cyclone had visited the place. It was most deplorable, and the travelers stood for some time as if trying to catch the true meaning of it all.

Finally their anxiety caused them to move forward and inspect the belongings.

“Good thing we didn’t have the treasure map,” remarked Mr. Lewis, examining the contents of a small black bag. “It wouldn’t be here now.”

At the end of their inspection the explorers found that nothing had been taken from their belongings. It appeared that the crafty Arabs wished only the treasure map, and that, not being able to find it, they had left without any other spoils.

“They sure acted in wild haste,” observed Mr. Holton. “It’s almost impossible to see how all this could have been torn up so quickly. It wasn’t five minutes from the time that you boys told of seeing the men that we were up here.”

“Trust the Arabs to do that,” said Dr. Kirshner, with a dry smile.

The scientists’ possessions were placed back in their proper places, and then they went to inspect the room occupied by Bob and Joe.

“Probably nothing taken from here, either,” was the opinion expressed by Mr. Holton, and he proved right, as they later found.

“This shows that these Arabs are desperate characters, and will probably stop at nothing,” said Dr. Kirshner, after a moment of thought. “We must be extremely careful to lock everything up from now on. It may even mean that we’ll have to watch ourselves, too.”

“What do you mean?” asked Joe.

“Simply that they may try to kidnap one or all of us to get possession of the map,” he replied in a low voice. “I know these natives. I’ve seen some of their actions before and feel sure that if these two men thought there was a good chance to get the map, they would try to do it.”

“It may not be as easy as they think,” said Bob, although he was a bit uneasy.

No more time was spent in the rooms, for they were all desirous of seeing more of the strange city and country.

“It might be wise to call on our Arabian friend first,” said Dr. Kirshner. “The one who knows about the treasure, I mean. We haven’t seen him since we left the ship last night, and he may be anxious to know what plans we have in mind.”

“Yes,” agreed Joe. “And while there we can warn him against these crooks. They may come on to him for the map, since they found that we haven’t it.”

First, however, the boys’ fathers and Dr. Kirshner wished to breakfast.

“And while they’re busy eating, suppose we go out,” suggested Joe. “We don’t need to stay but a few minutes.”

Bob agreed. He, like his friend, was anxious to observe the strangeness of this unusual city. If what he had heard was true, it would be something to be long remembered.

Out on the street the youths were at once impressed by the wide variety of races and costumes. Frenchmen, Italians, Spaniards, Mahonese, and Maltese all walked side by side, the majority in European garb. Arabs, or rather those who are commonly called Arabs, for they are a very mixed breed, sauntered along, clad in their long gowns and hlafa, which hung down over the face and sides of the head. Occasionally a Negro could be seen, although this was the exception rather than the rule.

“Sure have variety here,” smiled Joe. “There’s about every race imaginable present.”

In a short time the youths reached the Place du Gouvernement, or central square, and the busy scene of life was very interesting. On one side of the forum was the Mosque of Djema-el-Djedid and the Grand Mosquée, and on the others were stores, hotels, and cafés. Stretching away in the distance were the four great streets of the city.

Bob and Joe spent some time in one position, watching the throng of Arabs, soldiers, Jews, and others peculiar to this metropolis. Strange, the boys thought, that the people paid little or no attention to them. But this was probably due to the fact that hundreds of tourists visit the city each year.

“I’d like to visit some of the stores,” remarked Bob. “But we’d better get back to the hotel.”

“Yes. Our dads and Dr. Kirshner will probably be waiting for us.”

Reluctantly they made their way back and found that the scientists were ready to leave for the Arab friend’s hotel.

“We’ll trust that we’ll find him in his room, or in the lobby,” said Mr. Holton, as he and the others followed Dr. Kirshner.

“He’ll probably be there,” returned the archæologist. “He’s expecting us over this morning to talk over the best procedure to find the hidden treasure.”

The hotel in which the Arab was staying was but a short distance up the street and around the corner. The explorers were barely within sight of the building when a figure rushed madly out of the door and came toward them.

“Something the matter with that fellow?” asked Bob, surprised to see such haste from the native.

“Looks that way,” returned Mr. Holton. “He’s – By George! It’s our Arab friend. Wonder what has happened?”

A moment later the man was up to them, his face white, his hands trembling.

“The treasure map!” he cried in poor English. “It is gone!”

CHAPTER III
A Villainous Deed

AT the Arab’s dread remark it seemed for a moment that the explorers were going to sink through the street. Dr. Kirshner reeled, and the perspiration came out on Mr. Holton’s face. Mr. Lewis and the boys were spellbound.

Gone! Hundreds of dollars – yes, thousands. After all this anticipating the good fortune of finding the supposedly hidden treasure. The explorers could hardly believe it.

At last Dr. Kirshner got a grip on himself.

“Do you have any idea where the thieves went?” he asked of the Arab, whose name was Fekmah.

“No,” was the reply. “They have complete disappeared. I try see where they go, but could not. They gone when I got to my room.”

“When did you first notice that the map had been taken?” inquired Bob in an anxious voice.

“No more than ten minutes ago,” Fekmah answered. “I had gone out to stay but a moment, and when came back to my room the door open and map gone. I run around to back and look out, but they gone.”

“Gone!” echoed Mr. Lewis. “We should have warned Fekmah to be on the lookout. If Bob and Joe had discovered the suspicious actions of the rascals sooner, it would have given us time to do so. But the fact that nothing strange was noticed till the night we were to reach port gave us no time to tell it.”

“So you knew?” asked the Arab friend. “You knew that robbers were after the map?”

Dr. Kirshner nodded.

“They broke into our rooms this morning, but when they couldn’t find the map they left without taking anything else,” he said. “We were just going over to warn you to be on the lookout and guard the map closely when we saw you.”

The Arab scowled and gritted his teeth.

“Allah curse them!” he exclaimed, vexed all the more because of almost but not quite knowing in time. “It’s too late now to find them, and they prob’ly gone by now.”

“Gone where?” asked Mr. Holton.

Fekmah spread his hands apart in a wide gesture and then pointed to the south.

“To get treasure,” he said quietly.

“Then we’ll get there first!” exclaimed Dr. Kirshner. “No thieves will get ahead of us. I think it might be well to start on the journey at once – that is, if you can go that soon,” he said to the Arab, who nodded.

“But how will we know where to go without the map?” asked Mr. Lewis.

“I have general idea,” Fekmah returned. “I studied it so much that know about where go. And I can leave any time.”

“Fine!” blurted out Dr. Kirshner. “We’ll get our belongings together and leave tomorrow. But first let me introduce my friends. I don’t believe you’re acquainted with them,” and he proceeded to introduce the Arab to Mr. Holton, Mr. Lewis, and Bob and Joe.

“Now let us all come up to my room,” said Fekmah. “We can talk over plans for the treasure search. There are much things you should know.”

They walked on up the street to a comparatively large building and were led in the door and up the stairs by Fekmah.

“So this is the hotel where he’s staying,” said Bob, casting eager eyes about the place.

“Sure is luxurious,” remarked Joe. “It’s the best in town.”

The Arab’s room was halfway down the hall, and to it they went.

“Now sit down,” directed Fekmah, “and we will talk things over.”

They did so and then made ready for what the Arab had to say.

There was a short silence. Then Fekmah resumed the conversation.

“Like Dr. Kirshner said, we should leave at once if expect to find the hidden riches before the thieves get ahead of us,” he began, showing an unusual ability to speak English correctly. “There are two routes we can take to get to the edge of the desert. We can take the railroad to Oran and then to Figuig, or can get on train to Wargla.” He moved over to a small satchel and took out a cloth map, which he unfolded and laid on a small table that was in the middle of the room. The map was French, and although the naturalists and their sons had a slight knowledge of that language, Dr. Kirshner and Fekmah were the only ones who knew it thoroughly.

“I think we can make out enough to satisfy ourselves, though,” said Mr. Holton.

The Arab traced the one route and then the other, pointing out the possibilities of each one. The object was to take a train to the farthest point in the desert possible and start the expedition from there on camelback.

“Now,” continued Fekmah, “our destination is the Ahaggar Mountains. They are about seventeen hundred kilometers (about a thousand miles) from here. From what we measured, the best route is to go to Wargla and get camels from there. What you think?”

“I believe you’re right,” returned Dr. Kirshner. “That route is much shorter, and we’ll have less difficulty in finding our way from Wargla than from Figuig. Nearly all expeditions depart from Wargla, and there are numerous small settlements on the way to the Ahaggar Mountains. Can we get a train in the morning?”

The Arab nodded.

“There about three trains a day out,” he said. “I believe one leaves in morning, so we can get there easy.”

“Fine!” exclaimed Mr. Lewis. “Then we’ll leave now and get packed and be here for you early in the morning.”

Fekmah bowed.

“And I will make the stolen map over again from memory, as near as can,” he said.

They bade the Arab good-bye and left the hotel to get their belongings together. If they were to leave for the Sahara the next morning, a great deal of packing would have to be done.

“Don’t suppose there’s any use trying to find the thieves, is there?” asked Joe, as they approached their hotel.

Dr. Kirshner laughed unwillingly.

“They are probably halfway to the Sahara by now,” he returned, although he knew this to be an exaggeration.

When the explorers arrived at their rooms, Dr. Kirshner directed the preparations for the expedition, and the remainder of the day was spent in doing this. It seemed that the archæologist had forgotten his duties as a scientist and was thinking only of finding the hidden riches.

“If we are fortunate enough to find our objective, we will be paid many times the cost of the expedition,” he said.

“If those crooks don’t get ahead of us,” added Joe, with a grim smile.

“They won’t – not if we can help it,” blurted out Bob, fumbling his automatic.

At noon the adventurers stopped only a few minutes for a meal, so eager were they to finish the task of preparing for the expedition. They found it necessary to purchase much that they did not have, and the bazaars of Algiers were visited often for the unusual in the way of luxuries.

At last the work was completed, and all sat down to rest after the strain. Bob and Joe had had the experience once before of helping to make preparations for an expedition and knew what was expected of them.

“I wish we could take motion pictures of this city,” remarked Bob that evening. “But we’ve been instructed to wait till we start the journey in the Sahara.”

The next morning the explorers were up early, and after a bountiful breakfast they made their way to Fekmah’s hotel.

The Arab was expecting them and had finished making a second map. It was none too accurate, for he did it from memory, but it promised to be the only means between defeat and failure.

“You may wonder why I bothered to make more map,” he said to his friends. “But it possible that I forget some of the landmarks when we are on way, and this will – ”

“Come to the rescue,” interrupted Joe, smiling.

“And also,” Fekmah went on, “you may have this if anything should happen me.”

“Let’s hope nothing will,” said Bob.

“And now,” began Dr. Kirshner, “I’m going down to the railroad station and find out if we can get a train this morning. I’ll be back in a short time.”

“While he’s gone, suppose we go out,” suggested Joe to his chum. “There’s a lot we can see around here before we leave.”

“All right,” Bob replied. “But we don’t want to stay too long. There might be a train out in an hour.”

The youths decided to see the old section of the city, as they had heard from Dr. Kirshner that many points of interest were to be found there. It was but a few minutes’ walk to their objective, and they turned their eyes about.

As they were passing a café, Bob motioned for his friend to look inside.

A gray-haired, shriveled old man in torn clothing was strumming a guitar and walking from one end of the café to another, holding out a hand for money. But no one seemed inclined to give him any. Evidently this was a common occurrence, for the people paid little or no attention to the old beggar.

“I’ve half a mind to give him a break,” started Bob, but Joe pulled him back.

“If we want to see any of this town we’ll have to be at it,” Joe said, leading the way down the street.

The narrow ways were lined with shops and bazaars, offering the shopper a wide variety of commodities.

“But most of the things they sell you don’t want,” smiled Bob, glancing at a counter laden with coarse native food.

The youths noticed that certain streets were devoted to the selling of certain products. For instance, one avenue was lined with shops displaying brassware.

“It ought to be easy to find what you want,” grinned Joe. “Just walk down one street and you will have a large choice of the same thing.”

The boys spent nearly a half-hour in the native quarter. Finally Bob suggested that they get back to the hotel, and his friend was also in favor.

In a short time they were back in the hostelry and proceeded to go to their rooms. But they were scarcely at the doors when the sound of footsteps came to their ears. The next moment Dr. Kirshner came into view.

“Hello,” greeted Bob, and then his jaw dropped.

That something was wrong was evidenced by the frown that was on the archæologist’s face. His usual smile was absent.

“There’s been a wreck,” he said in an anxious voice. “The train has been wrecked. I guess we can’t get to Wargla so soon after all.”