They trudged on to the head of the canyon and explored most of the smaller ones opening into it. But no trace of human presence, either recent or remote, did they find anywhere. When night came on they returned to their camp somewhat disappointed that they had seen no sign of the two men. Early the next morning they started out again, and searched carefully through the remaining canyons that were tributary to the large one, climbed again to its head, and clambered over the ridge at its source. There they looked down the other side of the mountain, over a barren wilderness of jagged cliffs and yawning chasms, with here and there a little clump of scrub pines or cedars clinging and crawling along the mountain side. They examined the summit of the peak and walked a little way down the eastern slope, looking into the gorges and searching the scrub-dotted slopes until the sinking sun drove them back to their camp. But they found neither water, save some strongly alkaline springs, nor any trace of human beings. As they discussed the day's adventures over their supper, Tom said: "There must have been some reason why they killed that horse just where they did." "Yes," said Nick, "if they had moved their camp to some other canyon higher up, or on the other side of the mountain, they might just as well have driven the beast farther up before they killed it." "If they had wanted the meat down here," added Tom, "they wouldn't have driven it so far away. They must have wanted it right there." They looked at each other with a sudden flash of intelligence in their puzzled eyes and Nick thwacked his knee resoundingly. Then he spoke the thought that had burst into each mind: "There must be a trail up the canyon wall!" [Illustration: "YOU'VE NOTHING TO FEAR FROM ME. I'LL BE DEAD IN TEN MINUTES."--_p. 206_] Early the next morning they were examining more closely than they had done before the walls of the canyon near the carcass. On the right hand side, the same side on which was the canyon where they had their camp, they found a narrow ledge beginning several feet above the boulders which strewed the floor of the canyon at the base of the wall. They found that with care they could walk along it, although in some places it was so narrow that there was scarcely room for Tuttle's big bulk. Nick was in constant fear lest his friend might topple over, and finally insisted that Tom should go back and wait until he reached the top of the wall or the end of the ledge. Tuttle blankly refused to do anything of the sort.