With not so much as a growl or warning, he launched himself upon Lad. Straight at the tired old dog's throat he flew. Lad, all unprepared for such unheard-of mutiny, was caught clean off his guard. He had not even time enough to lower his head to protect his throat or to rear and meet his erstwhile subject's attack halfway. At one moment he had been plodding gravely toward his two supposedly loyal friends; the next, Rex's ninety pounds of whale-bone muscle had smitten him violently to earth, and Rex's fearsome jaws--capable of cracking a beef-bone as a man cracks a filbert--had found a vise-grip in the soft fur of his throat. Down amid a flurry of high-tossed snow, crashed Lad, his snarling enemy upon him, pinning him to the ground, the huge jaws tearing and rending at his ruff--the silken ruff that the Mistress daily combed with such loving care to keep it fluffy and beautiful. It was a grip and a leverage that would have made the average opponent helpless. With a short-haired dog it would have meant the end, but the providence that gave collies a mattress of fur--to stave off the cold, in their herding work amid the snowy moors--has made that fur thickest about the lower neck. Rex had struck in crazy rage and had not gauged his mark as truly as though he had been cooler. He had missed the jugular and found himself grinding at an enormous mouthful of matted hair--and at very little else; and Lad belonged to the breed that is never to be taken wholly by surprise and that acts by the swiftest instinct or reason known to dogdom. Even as he fell, he instinctively threw his body sideways to avoid the full jar of Rex's impact--and gathered his feet under him. With a heave that wrenched his every unaccustomed muscle, Lad shook off the living weight and scrambled upright. To prevent this, Rex threw his entire body forward to reinforce his throat-grip. As a result, a double handful of ruff-hair and a patch of skin came away in his jaws. And Lad was free. He was free--to turn tail and run for his life from the unequal combat--and that his hero-heart would not let him do. He was free, also, to stand his ground and fight there in the snowbound forest until he should be slain by his younger and larger and stronger foe, and this folly his almost-human intelligence would not permit. There was one chance and only one--one compromise alone between sanity and honor. And this chance Lad took. He _would_ not run. He _could_ not save his life by fighting where he stood. His only hope was to keep his face to his enemy, battling as best he could, and all the time keep backing toward home. If he could last until he came within sight or sound of the folk at the house, he knew he would be saved. Home was a full half-mile away and the snow was almost chest-deep. Yet, on the instant, he laid out his plan of campaign and put it into action.