One of the men knew the lay of the canyon. Its only practical outlet was that guarded by the sheepmen. But a short way up the canyon there was a spring in the hills, which found its outlet in a narrow stream that ended in a small waterfall at the edge of a cliff. Mart figured on his force entering the canyon, stampeding the sheep, and driving them over this waterfall. It was as simple as it was cruel, but you may have noticed that it takes clever people to think of simple things, and Mart Cooley was proving almost as clever with his mind as he was with his guns. For Mart also figured on the effect on the sheepmen's nerve when they found their herds gone, and their water from the tank giving out. Under cover of darkness Mart led about fifteen men around the hill, which they skirted, and, giving the ranch house a wide berth, made their way toward the mouth of the canyon. There was only one thing to guide them on their course. Where the western hills raised their heights toward the sky, their outline showed darker than the surrounding night. From this wall of black, Mart's force steered a diagonal course that would lead to the center of the canyon's mouth. Once in the canyon, out of range of the house and among the sheep, lanterns and fires would provide light enough for the men's purpose. It is not likely that there was an idea of poetic justice in the mind of Mart Cooley; a thought that in stampeding the sheep he was repaying the sheepmen in their own coin for stampeding the cattle, repaying them with the death of the victims added as interest. The plan seemed to be working out easily--too easily. Then, from one of the foremost rider's mounts, came the shrill neigh of a horse in pain, and the thudding of the animal's hoofs as it shied violently, for it had collided with the barbed wire fence. This was Mart's first intimation that there was a fence, but he had no time to think that he had been matched in cleverness by Donald Spellman, for things began to happen. First came the sound of a cowbell. At intervals along the lower strands of barbed wire bells had been hung. Next came a volley of shots, from the hills, which had been sought by the sheepmen under the cover of the night. They were firing toward the sound of the bells. The firing was not well-directed, but it was steady and dangerous. It is doubtful whether the attackers could have cut their way through the fence, handicapped as they were, but they had no chance to try, for just then a third thing happened. A cloud-obscured moon had been climbing the eastern hills, and at that moment the clouds parted and the entire valley was bathed in moonlight. The light was peaceful and beautiful, but it brought a deadly effect. Not only did it reveal the cattlemen to their enemies in the hills, but to those in the distant ranch house, as well. The cracking of rifles was almost continuous in that fatal triangle, in which the sheepmen formed two points, and the cowmen the tragic third.