"May the black monsters of Tidihet feast on them!" he exclaimed, running his fingers through his white hair. "Allah will punish them--they will not go free!" "But that won't help us any," said Mr. Lewis dryly. "We've got to figure out some way to stop them, if it's at all possible. The question is, what will it be?" "There's no way of telegraphing," said Dr. Kirshner, gazing thoughtfully at the floor. "If we had any idea where they went--that is, what route they took--we might overtake them on fast dromedaries. But the chances even then would be slight." "We might----" began Joe but was interrupted by a knock at the door. For a moment the adventurers looked at one another in surprise. Then Mr. Holton moved over and cautiously opened the door. The figure that stood in waiting was a tall, powerful Arab, with dark, piercing eyes that were none too pleasant to look at. He towered several inches above Mr. Holton, who was himself nearly six feet. Around the man's shoulders and reaching nearly to the floor was a white gown, and on his head was the conventional _hlafa_. For several moments he stood looking at the occupants of the room, as though forming a rapid opinion of the situation. Then he again turned to Mr. Holton and muttered something in the native tongue. That Bob's father understood was evidenced by the look of surprise that came on his face. A moment later he turned to his friends. "He says Fekmah is wanted by a friend," Mr. Holton said. "Won't say any more. I don't know what to make of it." "A friend?" Fekmah gasped. "Why, I know no person here. What could it mean?" Again the stranger said something in Arabic and motioned for his objective to come out. For a moment Fekmah was thoughtful. Then he decided to investigate. "I will be back in short minutes," he said and walked toward the door. "Wait a minute," called Dr. Kirshner. "I'm going with you." "And I, too," cried Bob, getting up from his chair. Joe also put in a request, but the archæologist shook his head. "Two more are enough," he said quietly, as he and Bob followed the Arab down the hall. "Be careful," warned Mr. Lewis, as they reached the stairs. "There's no telling what that fellow may want." They reached the street and were directed around the corner and up a narrow byway, the stranger remaining several yards in the van. "Keep a ready hand on your automatic," whispered Dr. Kirshner to Bob. "Something may happen in a short time now." "Do you believe Fekmah is really wanted by friends?" the youth asked, glancing about as if he expected any minute to be confronted by a band of desperate characters. "Beyond me," was the reply. "But I believe it would be safer to say no than yes. But there is a possibility that he met someone and has forgotten about it." "What could they want of him? It all seems funny to me." On they went, now upward by a gently sloping street that was so crooked it seemed to have no outlet.