Watching for a time, Sanderson made certain the man was not one of his own outfit, and then he shoved the muzzle of his rifle out, laid his cheek against the stock, and covered the partly exposed head of the man behind the boulder. Sanderson waited long with his cheek caressing the rifle stock, while the man behind the boulder wriggled farther out, exposing himself more and more in his eagerness to gain a more advantageous position. And presently, without moving his head, Sanderson discovered that it was Williams who was in danger. Williams had concealed himself behind a jagged rock, which protected him from the bullets fired from across the defile, and from the sides. But the rock afforded him no protection from the rear, and the man behind the boulder was going to take advantage of his opportunity. "That's my engineer, mister," he said grimly; "an' I ain't lettin' you make me go to the trouble of sendin' east for another. You're ready now, eh?" The man behind the boulder had reached a position that satisfied him. Sanderson saw him snuggle the stock of his rifle against his shoulder. Sanderson's rifle cracked viciously. The man behind the boulder was lying on a slight slope, and when Sanderson's bullet struck him, he gently rolled over and began to slide downward. He came--a grotesque, limp thing--down the side of the defile, past the engineer, sliding gently until he landed in a queer-looking huddle at the bottom, near the trail. Sanderson intently examined other rocks and boulders on the opposite side of the defile. He had paid no attention to Williams' "Good work, Sanderson!" except to grin and assure himself that Williams hadn't "lost his nerve." Presently at an angle that ran obliquely upward from a flat, projecting ledge, behind which another Double A man lay, partly concealed, Sanderson detected movement. It was only a hat that he saw this time, and a glint of sunlight on the barrel of a rifle. But he saw that the rifle, after moving, became quite motionless, and he suspected that it was about to be used. Again the cheek snuggled the stock of his rifle. "This is goin' to be some shot--if I make it!" he told himself just before he fired. "There ain't nothin' to shoot at but one of his ears, looks like." But at the report of the rifle, the weapon that had been so rigid and motionless slipped from behind the rock and clattered downward. It caught halfway between the rock and the bottom of the defile. There came no sound from behind the rook, and no movement. "Got him!" yelled Williams. "Go to it! There's only two more on this side, that I can see. They're trying mighty hard to perforate me--I'm losing weight dodging around here trying to keep them from drawing a bead on me. If I had a rifle----"