Thus Ruiz Gregorio Maria y Alvarez, lolling lazily in his saddle while the hard-breathing mustang picked a toilsome path among the strewn boulders and through the sliding shale beds. He went even further: an alibi might not be needful, but it would be easy to provide one. Young Jack Benson, if no other, would know that Ford had taken one of the shorter trails from Copah to the camp at Horse Creek. _Bueno!_ He, Ruiz Gregorio, could slip across the river in the dusk when the thing was done, skirt the headquarters camp unseen, and present himself a little later at Senor Frisbie's camp of the track-layers, coming, as it were, direct from Copah, almost upon the heels of Senor Benson. After that, who could connect him with the dead body of a man fished out of a river twenty, fifty, a hundred miles away? There was a weak link in the chain. Ruiz Gregorio's child-like plot turned upon one pivot of hazard--hazard most likely to be ignored by so good a marksman as the "man-killer." One shot he might permit himself, with little danger of drawing a crowd from the mess tent and the sleeping shanties in the Horse Creek camp. Two would bring the men to their doors. Any greater number would be taken as the signal of a free fight needing spectators. Hence the first shot must suffice. The Mexican bore this in mind when, arriving at his post opposite the camp in the early dusk, he chose his ambushing boulder so near the descending hill trail that a stout club might have been substituted for the pistol. The weather promise was for a starless night, but the electric arc-lights were already scintillating at their mastheads in the headquarters railroad yard across the Pannikin. Later, when the daylight was quite gone and the electrics were hollowing out a bowl of stark whiteness in the night, Ruiz Gregorio wished he had chosen otherwise. The camp lights shone full upon him and on the mustang standing with drooped head at his elbow, and the trail on the other side of the boulder was in shadow. He was about to take the risk of moving farther up the hill-path to a less exposed lurking place, was hesitating only because his indolent soul rebelled at the thought of having to drag Ford's body so many added steps to its burial in the river, when the clink of shod hoofs upon stone warned him that the time for scene-shifting had passed. Pushing the mustang out of the line of sight from the trail, he flattened himself against the great rock and waited.