Jack, on all fours, began to quarter over the ground like a bloodhound seeking a trail. Every sense in him seemed to quicken to the hunt. His alert eyes narrowed in concentration. His fingertips, as he crept forward, touched the sand soft as velvet. His body was tense as a coiled spring. No cougar stalking its prey could have been more lithely wary. For the Ranger had found a faint boot-track, and with amazing pains he was following this delible record of guilt. Some one had come here and looked at the dead body. Why? To make sure that the victim was quite dead? To identify the victim? Roberts did not know why, but he meant to find out. The footprint was alone. Apparently none led to it or led from it. On that one impressionable spot alone had been written the signature of a man's presence. But "Tex" Roberts was not an old plainsman for nothing. He knew that if he were patient enough he would find other marks of betrayal. He found a second track--a third, and from them determined a course to follow. It brought him to a stretch of soft ground at the edge of a wash. The footprints here were sharp and distinct. They led up an arroyo to the bluff above. The Ranger knelt dose to the most distinct print and studied it for a long time. All its details and peculiarities were recorded in his mind. The broken sole, the worn heel, the beveled edge of the toe-cap--all these fastened themselves in his memory. With a tape-line he measured minutely the length of the whole foot, of the sole and of the heel. These he jotted down in his notebook, together with cross-sections of width. He duplicated this process with the best print he could find of the left foot. His investigation led him next to the summit of the bluff. A little stain of blood on a rock showed him where Wadley had probably been standing when he was shot. The murder might have been done by treachery on the part of one of his companions. If so, probably the bullet had been fired from a revolver. In that case the man who did it would have made sure by standing close behind his victim. This would have left powder-marks, and there had been none around the wound. The chances were that the shooting had been done from ambush, and if this was a true guess, it was a fair deduction that the assassin had hidden behind the point of rocks just back of the bluff. For he could reach that point by following the rim-rock without being seen by his victim. Roberts next studied the ground just back of the point of rocks. The soil here was of disintegrated granite, so that there were no footprints to betray anybody who might have been hidden there. But Jack picked up something that was in its way as decisive as what he had been seeking. It was a cartridge that had been ejected from a '73[1] rifle. The harmless bit of metal in his hand was the receptacle from which death had flashed across the open toward Ford Wadley.