Finally, after trudging over a high plateau, they began climbing the base of the twin peaks. At first the ascent was very gradual, but in a short time the path curved upward around the side of the mountain. "Getting there, all right," observed Bob, as he noticed that they were now several hundred feet above the plateau. At last they came to the top of a wide ledge, from which they could look out over scores of miles of rugged country. As the shelf began to narrow, Bob called a halt. He took out the paper of native words and told the Tuaregs that they were now near the cave in which were his father and friends. It would only be necessary to round a corner before coming to its entrance. But first he divided the group of natives into two sections. One, under the command of the chieftain, was to move on around the ledge to the cave from the west. The other, led by himself, would climb the steep side of the mountain and walk on above to the other side of the cavern. Then they would meet at the entrance and surround the Arabs and release the prisoners. When Bob gave the word, the Tuaregs swung into action. Those in his group followed him up the cliff to the brink, while the men under the chieftain began moving around the ledge. It was a dangerous climb up the steep side of the mountain, but at last Bob pulled himself up to another ledge about fifty feet above the lower one. Then he led the way several rods along its surface. When he thought they had passed beyond the entrance to the cave, he led the descent to the lower shelf. A moment later he saw that he had miscalculated. He had not gone far enough beyond the cavern to escape the wary eyes of the Arabs who were stationed as guards. "Caught!" he exclaimed. "Caught square!" Four Arabs were sitting out in front, and they were on their feet instantly as their eyes fell on Bob. The latter was no more than twenty-five feet away from them, much nearer than he had expected to be. The Arabs' rifles were standing against the wall of rock near the cave. But before the men could get to them, Bob rushed forward. With a wild shout he kicked the rifles away and dashed into the cavern. Startled exclamations--exclamations of joy, surprise, happiness--came to the youth's ears, and he realized that he had at last found his father, Joe, and the others. "Bob! You here!" cried Mr. Holton in wild excitement. "You old rascal! I knew you'd get us out!" came from Dr. Kirshner. But there was no time for that. Danger was at hand. "Quick!" he commanded. "Hide. Here, take my rifle, somebody. I'll use my pistol. There's no time to lose!" The words were scarcely out of his mouth when the four Arabs darted inside the cave and made for the captives and their new enemy. They would not be beaten so easily! With a terrific crack to the chin, Bob sent the foremost Arab to the ground. The other three men were making for the prisoners in the back of the cave.