That night they made camp in a little cave that offered an asylum. The boys rather fancied the idea for a change. And they passed a very comfortable night without any alarm. Once, Bob being on duty near the mouth of the opening, heard a shuffling sound without. He could not make out whether it was caused by the passage of a human being, or a bear. Half believing that they were about to be attacked by some animal that fancied the cave as a den, he had drawn back the hammer of his rifle, and watched the round opening that was plainly seen at the time, as it was near morning, and the small remnant of a moon was shining without. But he waited in vain, and, as the minutes passed without any further alarm, Bob heaved a sigh of relief. It was all very well to think of shooting big game; but under such conditions he did not much fancy a close battle. When morning came, and he had told Frank about it, the other immediately went out to look for traces of the animal. As he came back Bob saw by the expression on his chum's face that Frank had made some sort of discovery. "How about it?" he asked. "It was no bear," replied the other, decidedly. "But sure I heard something moving, Frank, and I was wide-awake at the time, too," Bob protested. "I guess you were, all right," Frank admitted. "A man passed by, not far from the mouth of the cave. He even stooped down, and looked in, though careful not to let his head show against the bright background. Then he went off again up the canyon." "Since you know so much, Frank, perhaps you could give a guess as to who he was," said Bob, eagerly. "No guess about it," came the reply. "I've examined his track before, and ought to know it like a book. It was Abajo, Bob!" "Then ten to one, Spanish Joe and Eugene were close by!" declared Bob. "Say, do you really believe he knew we were in here?" "Of course he did," Frank asserted. "Perhaps they saw us enter. But Abajo also knows that both of us are fair shots. He did not dare take the chance of trying to creep in. It would be more dangerous than our going into that wolf den." "The plot seems to be thickening, Frank. It won't be long now before something is bound to happen. If we could only run across the old Moqui now, and hear that he carried a message in answer to your note, that would clear the air a heap, wouldn't it?" "Well, we must live in hopes," replied Frank, cheerfully. "And now, after a bite which Charley Moi is getting ready for us, we'll be off again, and tackle the roughest traveling in the whole canyon, so he says. But he knows the way, because he was led up here by the old professor, and told to come back every two months." CHAPTER XVII THE WINDOWS IN THE ROCKY WALLS "Well, here it's the fourth day we've been out, and nothing doing yet, Frank!"