The wolf trembled all over, struggling to get his meaning. This was no creature of subordinate intelligence: the great wolf of the North. He had, besides the cunning of the wild hunters, the intelligence that is the trait of the whole canine breed. Nor did he depend on his sense of hearing alone. He watched his master's face, and more than that, he was tuned and keyed to those mysterious vibrations that carry a message from brain to brain no less clearly and swift than words themselves,--the secret wireless of the wild. "He's my buddy, old boy, and I want you to find him for me," Ben went on, more patiently. He searched his pockets, drawing out at last the copy of the letter Ezram had given him that morning, and, because the old man had carried it for many days, it could still convey a message to the keen nose of the wolf. He put it to the animal's nostrils, then pointed away into the darkness. Fenris followed the motion with his eyes; and presently his long body stiffened. Ben watched him, fascinated. Then the wolf sniffed at the paper again and trotted away into the night. In one leap Ben was on his feet, following him. The wolf turned once, saw that his master was at his heels, and sped on. They turned up a slight draw, toward the hillside. It became clear at once that Fenris was depending upon his marvelous sense of smell. His nose would lower to the ground, and sometimes he tacked back and forth, uncertainly. At such times Ben watched him with bated breath. But always he caught the scent again. Once more he paused, sniffing eagerly; then turned, whining. Just as clearly as if they had possessed a mutual language Ben understood: the animal had caught the clear scent at last. The wolf loped off, and his fierce bay rang through the hushed forest. It was a long-drawn, triumphant note; and the wild creatures paused in their mysterious, hushed occupations to listen. It was also significant that it made certain deadly inroads in the spirit of Ray Brent, sitting in his distant cabin. He marked the direction of the sound, and he cursed, half in awe, under his breath. He had always hated the gray rangers. They were the uncanny demons of the forest. Ben followed the running wolf as fast as he could; and in his eagerness he had no opportunity for conjecture as to what he would find at the end of the pursuit. Yet he did not believe for an instant this was a false trail. The wolf's deep, full-ringing bays were ever more urgent and excited, filling the forest with their uproar. But quite suddenly the silence closed down again, seemingly more deep and mysterious than ever.