The fear grew. Try as he might he could not shake it off. It seemed to be gripping his heart with icy fingers, paralysing his every energy, and turning him into a craven coward. He started at his own footsteps. The shadow of a boulder, cast in a grotesque, distorted form by the fungi light upon the ground at his feet, brought him up with a jump, and only with great difficulty did he restrain a cry. The valley seemed to grow full of strange sounds. Ghostly voices whispered in his ears, hideous faces peered out from the shelter of the fungi. He was in the grip of a terror such as he had never known before! Then, upon the heels of this wholly imaginary fear, came a real one. Footsteps--stealthy, all but noiseless footsteps--sounded behind him, He glanced backward. A score of yards behind him a black shadow was moving, a shapeless smudge against the green of the moss. For one terrible instant his heart seemed to stop beating. What was the _Thing?_ Nearer it crept, sliding from shadow to shadow with a sinister movement horrible to witness. And still the lad stood motionless, his very soul withered by the fear that gripped him. Nearer still--but a few feet separated the thing from the engineer; then the latter recovered the use of his limbs, and, with a wild yell of terror, dashed madly down the valley. As he did so, the creature behind rose from its crouching position, disclosing to view the hideous form of a wolf-man. A moment the savage stood gazing after the rapidly-vanishing Wilson, then, picking up something the latter had dropped, he turned without troubling to give chase, and, plunging in among the fungi, disappeared. Like a hunted stag Wilson bounded over the ground, all other thoughts lost in the one mad desire to get away from the creature behind. He never turned to look if the brute was following. He rushed on blindly, madly, the fear that gripped him lending him fictitious strength. He knew nothing, saw nothing, until, utterly exhausted, his trembling limbs refused to carry him farther, and he dropped full length upon the ground. A long while he lay where he had fallen, too wearied to move, thoroughly disgusted with himself for so allowing fear to overcome him. When at last he arose he was astonished at his surroundings. Although he had no recollection of so doing, he must, in his flight, have emerged from the valley of bones, for he was in a gloomy defile, between towering cliffs. From which direction he had come he could not tell, but, trusting to luck, he strode forward into the darkness of the defile. His terror had gone, but it had left him weak and trembling as with an ague. Not a single fungus grew in the gloomy gorge; not even the twilight peculiar to this strange subterranean world relieved its dark obscurity. Yet, despite this absence of light, Wilson felt safer than amid the fungi. If the darkness concealed dangers, it also hid him from the sight of Lurking enemies.