The next moment the vivid moon was suddenly obscured by drifting wisps of cloud. As the green light blurred to an emerald haze, the creature under the crag came slithering out toward Dixon. He had a vague glimpse of a monster such as one should see only in nightmares--a huge loathesome spider-form with a bloated body as long as that of a man, and great sprawling legs that sent it half a dozen yards nearer Dixon in one effortless leap. * * * * * The onslaught proved too much for Dixon's morale, half-dazed as he was by the green moon's paralyzing rays. With a low inarticulate cry of terror, he turned and ran, straining every muscle in a futile effort to distance the frightful thing that inexorably kept pace in the shadowy emerald gloom behind him. Dixon's strength faded rapidly after his first wild sprint. Fifty yards more, and his faltering muscles failed him utterly. The dread rays of that grim green moon sapped his last faint powers of resistance. He staggered on for a few more painful steps then sprawled helplessly to the ground. His brain hovered momentarily upon the verge of complete unconsciousness. Then he was suddenly aware of a fluttering struggle, inside his tunic where he had placed the body of the quail. A moment later and the bird wriggled free. It promptly spread its wings and flew away, apparently as vibrantly alive as before the mysterious paralysis had stricken it. The incident brought a faint surge of hope to Dixon as he dimly realized the answer to at least part of the green moon's riddle. The bird had recovered after being shielded in the lead-cloth of his tunic. That could only mean one thing--the menace of those green moon rays must in some unknown way be radioactive. If Dixon could only get the lead-cloth hood over his own head again he also might cheat the green doom. He fumbled at the garment with fingers that seemed as stiff as wooden blocks. There was a long moment of agony when he feared that his effort had come too late. Then the hood finally slipped over his head just as utter oblivion claimed him. * * * * * Dixon came abruptly back to life with the dimly remembered echo of a woman's scream still ringing in his ears. For a moment he thought that he was awakening on his cot back in the laboratory after an unusually vivid and weird nightmare. Then the garish green moonlight around him brought swift realization that the incredible happenings of the night were grim reality. The clouds were gone from the moon, leaving his surroundings again clearly outlined in the flood of green light. Dixon lifted his head and cautiously searched the scene, but he could see no trace of the great spider-form that had pursued him.