"Fekmah," he cackled gently and then bent over and felt of the Arab's heart. It was still beating, and with a swift motion of a small knife Bob cut the ropes that bound the man. Then he removed the gag and stood back to see if his friend had been injured. The Arab's eyes opened, and he sat up with a start. A moment later the look of fear vanished from his face as he saw Bob. "Praise be to Allah!" he murmured, getting feebly to his feet. "Are you hurt?" the youth asked. "No--not yet," was the grim reply. "But the evil-doers were going to come back and kill me if I not tell where to find treasure. It is time now that they come. Let us go in haste, or they will stab us." "Treasure?" cried Bob. "You mean they wanted you to tell where the hidden riches in the desert are?" "Yes. They were going torture me if I not tell. They are demons. Allah curse them!" "But how did they know?" demanded Bob. "How did they find out about it? They're not the same ones who wrecked the train, are they?" Fekmah shook his head. "How they find out, I not know," he said. Cautiously they made for the door and opened it. Satisfied that there was no one in sight, they walked through the hallway and into the alcove. "Now we must be careful," Bob warned. "I knocked a man out a while ago, and he may have come to by now." But when they reached the place, they found the fellow still limp. At sight of the Arab, Fekmah looked at Bob with admiration. It was evident that the youth had gone beyond his expectations. In a short time they reached the door into the first room and found that Dr. Kirshner was still guarding the Arabs. The scientist looked up in relief when he again saw Bob and Fekmah. "I feared something had happened to you," the scientist said. "I shouldn't have allowed you to go in there," he said to Bob. "But I see you've done your duty and brought back Fekmah." "But what shall we do now?" Bob asked. "Are there any officers to take charge of these crooks?" "Yes," the archæologist returned. "You and Fekmah stay here and guard these men and I will go after them. It is best not to take them down to the police station for fear of attracting too much attention. Other Arab friends might charge us in a large band." The next moment he was gone, after having promised that he would be back with officers in a few minutes. "There ought to be some way to get the fellow I knocked out in here," Bob thought, as he guarded the Arabs closely. "But I'd better not risk letting Fekmah have the gun. I'll trust the fellow is still out of his senses when Dr. Kirshner and the officers arrive." The Arabs whom the youth was guarding were silent, but their evil faces suggested what they would do if given the chance. Bob was in a position where he could also watch the door in the next room. He was taking no chances on an attack from behind. "I bet Dad and the others are worried," the boy thought. "We've been gone a long time."