Ud tasted the scent of a man and sluggishly rolled his bullet head from shoulder to shoulder as he tried to catch sight of his ages-old enemy. For between the hairy quarter-ton beast men of the jungles of Sekk and the golden men of the valley cities who enslaved them there was eternal war. A growl rumbled deep in the hairy half-man's chest. He could see no enemy and yet the scent grew stronger with every breath. "You hunt too near the lake," called a voice. "The demons of the water will trap you." Ud's great nostrils quivered. He tasted the odor of a friend mingled with that of a strange Zuran. He squatted. "It's Noork," he grunted. "Why do I not see you?" "I have stolen the skin of a demon," answered the invisible man. "Go to Gurn. Tell him to fear the demons no longer. Tell him the Misty Ones can be trapped and skinned." "Why you want their skins?" Ud scratched his hairy gray skull. "Go to save Gurn's ..." and here Noork was stumped for words. "To save his father's woman woman," he managed at last. "Father's woman woman called Sarna." And the misty blob of nothingness was gone again, its goal now the marshy lowlands that extended upward perhaps a thousand feet from the jungle's ragged fringe to end at last in the muddy shallows of the Lake of Uzdon. To Noork it seemed that all the world must be like these savage jungle fastnesses of the twelve valleys and their central lake. He knew that the giant bird had carried him from some other place that his battered brain could not remember, but to him it seemed incredible that men could live elsewhere than in a jungle valley. But Noork was wrong. The giant bird that he had ridden into the depths of Sekk's fertile valleys had come from a far different world. And the other bird, for which Noork had been searching when he came upon the golden-skinned girl, was from another world also. The other bird had come from space several days before that of Noork, the Vasads had told him, and it had landed somewhere within the land of sunken valleys. Perhaps, thought Noork, the bird had come from the same valley that had once been his home. He would find the bird and perhaps then he could remember better who he had been. So it was, ironically enough, that Stephen Dietrich--whose memory was gone completely--again took up the trail of Doctor Karl Von Mark, last of the Axis criminals at large. The trail that had led the red-haired young American flier from rebuilding Greece into Africa and the hidden valley where Doctor Von Mark worked feverishly to restore the crumbled structure of Nazidom, and then had sent him hurtling spaceward in the second of the Doctor's crude space-ships was now drawing to an end. The Doctor and the young American pilot were both trapped here on this little blob of cosmic matter that hides beyond the Moon's cratered bulk.