Chet was racing across the rocks; the pistol was in his hand. What fearful thing would he face? What was it that had attacked? He forced his leaden feet to carry him on in a succession of wild leaps. Forgotten was the menace behind him, although he half saw, half sensed, a shadow that moved faster than he along the upper rocks. He thought only of the unknown horror that was ahead, that had drawn that despairing shriek from the brave lips of Diane. The few seconds of his crossing were an age in length. One last spring, one vivid instant while the Earth-light marked in sharp distinctness the figure of a leaping man! It was Harkness, throwing himself into the air, trying vainly to reach the struggling form of Diane Delacouer. She was held high above his head, and she was wrapped in the coils of a monster serpent--coils that finished in a smoothly-rounded end. And Chet knew in that instant of horror that the thing was headless! He was raising his pistol to fire; the long moments that seemed never to end were in actuality an instant. Where should he aim? He must not injure Diane. From the high rocks beside him came a glint of light, a straight line of reflected brilliance as from a poised and slender shaft. It moved, it flashed downward, it hissed angrily as it passed close to Chet's head. It went on, a spear like a flash of light--on and down, to drive sharply into the body of that serpent shape! And the coils, at that blow, relaxed, while the figure of Diane Delacouer fell limply to the outstretched, cushioning arms of the man below.... * * * * * Had the weapon been thrown with uncanny accuracy, or had it been meant for him? Chet could not be sure. But he knew that before him Walt Harkness was bending protectingly above the unconscious figure of a girl, while above and about the two there flailed a terrible, headless thing that beat the rocks with sledge-hammer blows. It struck Harkness once and sent him staggering, and once it came close to Chet so that his hands closed upon it for an instant. And with the touch he knew that this serpent was no animal shape, but worse--a creeping tendril from some flesh-eating horror of the vegetable world. He dashed in beside Walt; he saw Kreiss hurrying across the rocks. They had Diane safely out of reach of the threshing, striking thing before the scientist arrived. The spear that had passed close to Chet had pinned this deadly thing to earth; it tore loose as they watched, and the wounded tendril, with the spear still hanging from its side, slid swiftly down the slope and into the darkness at the foot of the rocks.