There was only one weak spot in the programme, the Black Stallion, the cause of the hunt, seemed made of iron, that ceaseless swinging pace seemed as swift and vigorous now as on the morning when the chase began. Up and down he went rounding up the herd and urging them on by voice and example to escape. But they were played out. The old white mare that had been such help in sighting them at night, had dropped out hours ago, dead beat. The half-bloods seemed to be losing all fear of the horsemen, the band was clearly in Jo's power. But the one who was the prize of all the hunt seemed just as far as ever out of reach. Here was a puzzle. Jo's comrades knew him well and would not have been surprised to see him in a sudden rage attempt to shoot the Stallion down. But Jo had no such mind. During that long week of following he had watched the horse all day at speed and never once had he seen him gallop. The horseman's adoration of a noble horse had grown and grown, till now he would as soon have thought of shooting his best mount as firing on that splendid beast. Jo even asked himself whether he would take the handsome sum that was offered for the prize. Such an animal would be a fortune in himself to sire a race of pacers for the track. But the prize was still at large--the time had come to finish up the hunt. Jo's finest mount was caught. She was a mare of Eastern blood, but raised on the plains. She never would have come into Jo's possession but for a curious weakness. The loco is a poisonous weed that grows in these regions. Most stock will not touch it; but sometimes an animal tries it and becomes addicted to it. It acts somewhat like morphine, but the animal, though sane for long intervals, has always a passion for the herb and finally dies mad. A beast with the craze is said to be locoed. And Jo's best mount had a wild gleam in her eye that to an expert told the tale. But she was swift and strong and Jo chose her for the grand finish of the chase. It would have been an easy matter now to rope the mares, but was no longer necessary. They could be separated from their black leader and driven home to the corral. But that leader still had the look of untamed strength. Jo, rejoicing in a worthy foe, went bounding forth to try the odds. The lasso was flung on the ground and trailed to take out every kink, and gathered as he rode into neatest coils across his left palm. Then putting on the spur the first time in that chase he rode straight for the Stallion a quarter of a mile beyond. Away he went, and away went Jo, each at his best, while the fagged-out mares scattered right and left and let them pass. Straight across the open plain the fresh horse went at its hardest gallop, and the Stallion, leading off, still kept his start and kept his famous swing.