“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!”