Putting out of the fight the man who lay pressed beneath his horse had been a necessary preliminary, a colorless detail, a smoothing away of a small annoyance in the road of that hour's great work. For the end was justified beforehand between him and Hall. It was not a matter of vengeance, but of justice. This man had once attempted to take away his life by the most diabolical cruelty that human depravity could devise. This passed through Mackenzie's thoughts like the heat of a fire that one runs by as he swung round to face Hall. Apparently unconcerned by what had befallen his friend, Hall was circling Reid's dead horse, holding tenaciously to his intention of clearing the ground before him as he advanced. Reid snaked himself on his elbows ahead of his enemy's encircling movement, keeping under cover with admirable coolness and craft. Mackenzie ran forward, throwing up his hand in command to Hall, challenging him as plainly as words to turn his efforts from a defenseless man to one who stood ready to give him battle. Hall drew off a little from Reid's concealment, distrustful of him even though he must have known him to be unarmed, not caring to put a man behind his back. Still drawing off in that way, he stopped firing to slip more cartridges into his automatic pistol, watching Mackenzie's rapid advance, throwing a quick eye now and then toward the place where Reid lay out of his sight. Hall waited in that sharp pose of watchful indecision a moment, then spurred his horse with sudden bound toward Reid. He leaped the carcass of Reid's animal at a gallop, firing at the man who huddled close against its protection as he passed over. Mackenzie could not see Reid from where he stood, but he felt that his peril was very great, his chances almost hopeless in the face of Hall's determination to have revenge on his brother's slayer in defiance of what might come to himself when the thing was done. Mackenzie ran a little nearer, and opened fire. Heedless of him, Hall swung his horse back at a gallop, firing at Reid as he advanced. Reid came rolling round the carcass of his horse to place himself in the protection of the other side, so nimble in his movements that Mackenzie drew a breath of marveling relief. If Reid was touched at all by Hall's vicious rain of lead, it could be only slightly. Hall's headlong charge carried him several rods beyond Reid, the horse springing high over the barrier. Again Reid escaped, again he came rolling back to shelter, his body as close to the ground as a worm's. When Hall pulled up his sliding, stiff-legged horse and turned in the cloud of dust to ride once more upon his defenseless enemy, it was to face Mackenzie, who had run up and posted himself directly in his way.