His own kind, yet he was worried, for he connected horses inevitably with the thought of man.  Nevertheless, he decided to explore, and coming warily over a rise of ground he saw, in the hollow beyond, a whole troop of horses without a man in sight.  He was too wise to jump to conclusions but slipped back from his watch-post and ran in a long semi-circle about the herd, but having made out that there was no cowpuncher nearby, he came back to his original place of vantage and resumed his observations.

A beautiful black stallion wandered up-wind from the rest and another, younger horse, was on the other side of the herd.  Between was a raggedly assembled group of mares old and young, with leggy yearlings, deer-footed colts, and more than one time-worn stallion.  It was a motley assembly.  The colors ranged from piebald to grey and there was a great diversity in stature.  Presently the black stallion neighed softly, whereat the rest of the herd bunched closely together, the mares with the foals on the side, and all heads turning towards the black who now galloped to a hilltop, surveyed the horizon and presently dropped his head to graze again.

This was a signal to the others.  They spread out again carelessly, but Alcatraz was beginning to put two and two together in his thoughts.  The two stallions were obviously guards, but what should they be guarding against in the broad light of day except that terrible destroyer who hunts as well at noon as at midnight—­man!  Inspiration came to Alcatraz.  The difference of color and stature, the unkempt manes and tails, the wild eyes, were all telling a single story, now.  These were not servants to man, and since they were not his servants they must be enemies, for that was the law of the world.  The great enemy dominated, and where he could not dominate he killed.  And the herd feared the same power which Alcatraz feared; instantly they became to him brothers and sisters, and he stepped boldly into view.

The result was startling.  From the hilltop the black stallion whinnied shrill and short and in a twinkling the whole group was in motion scurrying north.  Alcatraz looked in wonder and saw the black fall in behind the rest and range across the rear biting the flanks of older horses who found it difficult to keep the hot pace.  With this accomplished and when the herd was stolidly compacted before his driving, the black skirted around the whole group and with a magnificent spurt of running placed himself in the lead.  He kept his place easily, a strong galloping grey mare at his hip, and from time to time tossed his head to the side to take stock of his followers.  And so they dipped out of sight beyond the next swell of ground.

Alcatraz recovered from his amazement to start in pursuit.  This was a mystery worth solving.  Moreover, the moment he made sure that these were not man-owned creatures they had become inexplicably dear to him and as they disappeared his heart grew heavy.  His running gait carried him quickly in view.  They had slackened in their flight a little but as he hove in sight again they took the alarm once more, the foals first rushing to the front and then the whole herd with flying manes and tails blown straight out.