"If I can only make that little canyon," the youth thought, bending low so as to lessen the wind resistance. The canyon was near now, but a hurried look over his shoulder told Bob that the Arabs were near also. If he could only get there! He lashed the dromedary with a new determination and entered the narrow way between the mountains just as the Arabs passed over a small grove of low shrubs some two hundred feet away. Bob knew that this was a very short canyon and that there were numerous large rocks and crevices at the opposite end. Perhaps he could successfully evade his pursuers by hiding in one of these openings in the mountainsides. Sharp jagged crags protruded from all sides of the thread-like passageway between the high walls. It was very dangerous to ride with much speed in such a place, but the chance had to be taken. He reached the other end of the passage with but a moment to spare. Immediately his dromedary was cut over to the right behind a barrel-like rock. But the youth did not stop there; he wound in and out among the many huge boulders. At last he came to a stop in a large crevice between two imposing slabs of stone. With every nerve on edge, the young man listened. "They're coming!" he thought, getting out his revolver. "But they won't get me if I can help it!" But he was in a very secure hideout, and it was unlikely that the Arabs would locate it. Still he realized that they probably knew this region better than did he. As Bob waited breathlessly, his mind was in a whirl. Who were these Arabs? What did they want? Why had they descended upon the little exploring party so mysteriously? Bob did not know what to make of the situation, but he knew that danger was at hand. What further added to his perplexity was the fact that Arabs did not normally inhabit the Sahara so far south as this. Suddenly he started, as a thought struck him. Was it--the two thieves who stole Fekmah's map? Entirely possible, of course. Then a strange thing happened. As though informed by some unseen power, Bob grasped the whole situation. He saw Dr. Kirshner and Joe in the clutches of the two thieves, being held as prisoners. He visioned his father, Mr. Lewis, and Tishmak riding away under the guard of the Arabs. "Those thieves did it, then, to keep us away from the hidden treasure," thought the youth, and he could not have had a more accurate realization. For some time he listened closely for any sound from the two Arabs who had pursued him. He thought once he heard the footsteps of camels, but was not sure. What was he to do next? He was now doubly glad that good fortune had enabled him to escape from the would-be captors. If the Arabs had been nomad plunderers, he would probably not have suffered much by remaining with his father and the others. But as it was, there was a possibility of bringing rescue to his friends. "How am I to do it?" the youth mused, trying to remain calm.