By-and-by he found himself listening eagerly for the monotonous repetition of the prairie scavenger’s dismal howl, and as the cries recurred they seemed to grow in power and become more plaintively horrible.  Now, too, the sighing of the breeze drew more keen attention from the imprisoned man, and fancy magnified it into the sound of many approaching feet.  These matters were the effect of solitude.  At such times nerves play curious pranks.

In spite of his position, in spite of his anxiety of mind, the police-officer began to grow drowsy.  The long night’s vigil was telling, and nature rebelled, as she always will rebel when sleep is refused and bodily rest is unobtainable.  A man may pace his bedroom for hours with the unmitigated pain of toothache.  Even while the pain is almost unendurable his eyes will close and he will continue his peregrinations with tottering gait, awake, but with most of his faculties drowsily faltering.  Horrocks found his head drooping forward, and, even against his will, his eyes would close.  Time and again he pulled himself together, only the next instant to catch himself dozing off again.

Suddenly, however, he was electrified into life.  He was awake now, and all drowsiness had vanished.  A sound—­distant, rumbling, but distinct—­had fallen upon his, for the moment, dulled ears.  For awhile it likened to the far-off growl of thunder, blending with a steady rush of wind.  But it was not passing.  The sound remained and grew steadily louder.  A minute passed—­then another and then another.  Horrocks stared in the direction, listening with almost painful intensity.  As the rumbling grew, and the sound became more distinct, a light of intelligence crept into the prisoner’s face.  He heard and recognized.

“Cattle!” he muttered, and in that pronouncement was an inflection of joy.  “Cattle—­and moving at a great pace.”

He was alert now, as alert as he had ever been in his life.  Was he at last going to discover the coveted secret?  Cattle traveling fast at this time of night, and in the vicinity of the great keg.  What could it mean?  To his mind there could only be one construction which he could reasonably put upon the circumstance.  The cattle were being “hustled,” and the hustler must be the half-breed Retief.

Then, like a douche of cold water, followed the thought that he had been purposely made a prisoner at the edge of the muskeg.  Surely he was not to be allowed to see the cattle pass over the mire and then be permitted to go free.  Even Retief in his wildest moments of bravado could not meditate so reckless a proceeding.  No, there was some subtle purpose underlying this new development—­possibly the outcome was to be far more grim than he had supposed.  He waited horrified, at his own thoughts, but fascinated in spite of himself.

The sound grew rapidly and Horrocks’s face remained turned in the direction from which it proceeded.  He fancied, even in the uncertain light, that he could see the distant crowd of beasts silhouetted against the sky-line.  His post of imprisonment was upon the outskirts of the bush, and he had a perfect and uninterrupted view of the prairie along the brink of the keg, both to the north and south.