Just below him he could discern the outline of his horse, with head lowered, evidently dozing. Having in mind the keenness of desert-bred stock, he watched the horse. The minutes drifted by. The horse seemed more distinct. Waring thought he could discern the picket rope. He endeavored to trace it from horse to picket. Foot by foot his eyes followed its slack outline across the ground. The head of the metal picket glimmered faintly. Waring closed his eyes, nodded, and caught himself. This time he traced the rope from picket to horse. It seemed a childish thing to do, yet it kept him awake. Did he imagine it, or had the rope moved? Dex had lifted his head. He was sniffing the cool morning air. Slowly the tawny-golden shape of the big buckskin turned, head up and nostrils rounded in tense rings. Waring glanced across the cañon. The farther wall was still dim in the half-light. In a few minutes the trail would become distinct. Dropping from the ledge, he stepped to his saddle. Dex evidently heard him, for he twitched back one ear, but maintained his attitude of keen interest in an invisible something--a something that had drawn him from drowsy inanition to a quietly tense statue of alertness. The ash gray of the farther wall, now visible, slowly changed to a faint rose tint that deepened and spread. Waring stooped and straightened up, with his glasses held on the far trail. A tiny rider appeared in the clear blue circle of the binoculars, and another, who led two horses without saddles or packs. The men were headed south. Presently they disappeared behind a wall of brush. Waring saddled Dex, and, keeping close to the eastern wall, rode toward the arroyo. The morning sun traced clean, black shadows of the chaparral on the sand. The bloom of cacti burned in red and yellow blotches of flame against its own dull background of grayish-green. At the mouth of the arroyo, Waring dismounted and dropped the reins. Dex nosed him inquiringly. He patted the horse, and, turning, strode swiftly down the dry river-bed. He walked upright, knowing that he could not be seen from the trail. He could even have ridden down the arroyo unseen, and perhaps it was a senseless risk to hunt men afoot in this land. The men he hunted were Mexicans of Sonora; fugitives. They would fight blindly, spurred by fear. Waring's very name terrorized them. And were they to come upon the gringo mounted, Waring knew that there was more than a chance his horse would be shot. He had a peculiar aversion to running such a risk when there was half a chance of doing his work on foot.