He had searched every foot of the home place himself that day for the two of Old Man Conlan, and had found not so much as a sheltered gulch, a hidden pocket. What, then, could Cattle Kate do with such a bunch as was coming up her trail now? Sheriff Selwood had food for thought but little time to use it. He had only time for decision, and for the action which was to follow swiftly on that decision. As the cattle came up the slope, pushed by the many horsemen who completely encircled them, they left a broad trail, their tracks all going upward—all this passed through his racing mind. What was to prevent him or any one else from riding straight up to their destination by broad daylight? And then on the heels of this question came like a flash of light on a dark curtain that old _coincidence in time_! When that ninety head had vanished Kate Cathrew had been driving down—driving _down_ from Sky Line—three hundred head, head of her own stock, all open and above board, properly branded clear and fair! Three hundred head of steers whose moiling hoofs, going down, would trample out all trace of ninety going up! The sheriff’s eyes were gleaming in the dark, his lips were a tight line of determination. He was beginning to get hold of the mystery with a vengeance. He thought of the windy passage that opened into Blue Stone Cañon. If he could only find its head he would, as Smith had said, have solved the problem. And unless he missed his guess by a thousand miles, those steers streaming past him at the moment were headed for it now! Here was the chance for which he had waited, for which he had ridden the hills for months, for which he had endured the contempt and the insinuations of the cattlemen. Here was the chance to nail her crimes on Cattle Kate Cathrew, to make the “killing” of his years of failure in office—and Sheriff Price Selwood, brave man and honest officer of the law, took his life in his hand again and fell in beside the herd. Dark, quiet, shadowy—he was a rider among the riders, to all intents and purposes one of Kate Cathrew’s men—and he was helping to drive Bossick’s steers up to the foot of Rainbow Cliff! From the few low-toned shouts and oaths he was able to identify the two men nearest him as Sud Provine and Caldwell, the foreman. He thanked his stars for his own dark horse, his inconspicuous clothing. It was hard going up the steep slants of Mystery Ridge, and kept every one busy to keep the cattle, unaccustomed to night driving and in strange country, headed in the right direction and all together. But they did the trick like veterans and after a long, hard drive, Selwood saw the rimrock of Rainbow Cliff against the stars. The herd was headed straight for the face of the cliff, and he expected soon to see the riders swing them east toward the corrals of Sky Line, but they did not do so. When the foremost steers were close under the wall Caldwell rode near and called to him, thinking him one of his men: