"Murder," Rock exclaimed, shortly; then he heaved his sled into motion once more, for 'Poleon had started his team and was making off through the town. Down into the bed of the smaller stream the pursuers made their way and up this they turned. Again they urged their dogs into a run. It took some effort to maintain a galloping pace now, for the teams were tiring, and after some mental calculations Rock shook his head doubtfully. Of course, his quarry was at a disadvantage, there being two men to one sled, but--twenty-three miles, with a two-hour start! It was altogether too great a handicap. The lieutenant had figured on that last forty miles, the last five or ten, in fact, but this change of direction had upset all his plans and his estimates. Evidently the McCaskeys cared not how nor where they crossed the Line, so long as they crossed it quickly and got Canadian territory behind them. Barring accident, therefore, which was extremely unlikely, Rock told himself regretfully that they were as good as gone. Two hours! It was too much. On the other hand, he and 'Poleon now had a fresh trail to follow, while the fleeing brothers had unbroken snow ahead of them, and that meant that they must take turns ahead of their dogs. Then, too, fifty miles over drifted trails at this season of the year was a heavy day's work, and the McCaskeys must be very tired by now, for neither was in the best of condition. In the spring, when the snows were wet and sled runners ran as if upon grease, such a journey would have been no great effort, but in this temperature the steel shoes creaked and a man's muscles did not work freely. Men had been known to play out unexpectedly. After all, there was a possibility of pulling them down, and as long as there was that possibility the Mounted Policeman refused to quit. Rock assured himself that this flight had established one thing, at least, and that was Pierce Phillips' innocence of the Courteau killing. The murderers were here; there could be no doubt of it. Their frantic haste confessed their guilt. Friendship for the boy, pride in his own reputation, the memory of that ovation he had received upon leaving, gave the officer new strength and determination, so he shut his teeth and spurred his rebellious limbs into swifter action. There was no longer any opportunity of riding the sled, even where the trail was hard, for some of the Police dogs were limping and loafing in their collars. This was indeed a race, a Marathon, a twenty-three-mile test of courage and endurance, and victory would go to him who could call into fullest response his last uttermost ounce of reserve power. Doret had promised that he would show his trail-mate how to travel, and that promise he had made good; all day he had held the lead, and without assistance from the lash. Even now his dogs, while not fresh, were far from exhausted. As for the man himself, Rock began to feel a conviction that the fellow could go on at this rate eternally.