He sensed it now in the sudden dryness of his mouth, the hammering of his heart as his adrenal glands surcharged his blood. Then away in the distance, he heard the winding of a horn! At least, it sounded like a horn. His hands tightened about the carbine and he held his breath. But though he listened for some time, the sound wasn't repeated. Gradually, the valley narrowed. Tall cliffs towered above him like the jaws of a vise. He had gone about five miles, the limit he had set himself for the first day, when he caught the sound of splashing mingled with laughter. He stopped in midstride, his nerves atingle. The sounds went on punctuated by giggling screams. He slid the safety off the carbine, crept forward. A hundred meters upstream the jungle on the opposite bank gave way to meadows that swelled up to meet the talus at the foot of a towering thousand foot cliff. Where the meadow dipped down to the stream there was a little gravel beach, and a band of women and children were splashing in the shallow water. Jupiter stood stock still, peering out from the forest like a tiger. The women were tall, brown-skinned, their hair wet and glistening like seals. Naked children squealed and played among the pebbles of the beach. His glance strayed beyond them to the cliffs, which were pitted by cave mouths, broken by ledges. He could distinguish the figures of men and women in breechclouts and skins clinging to the face of the rock like flies. These people had neither the brutish look of the green-skinned slaves he'd seen last night, nor yet the ferocity of the warriors. He felt the hot sluggish breeze shift, blowing from him towards the bathers. Instantly, the women were thrown into a panic. Those with children snatched them up, and the whole pack broke from the water, fled screaming towards the cliffs! Jupiter Jones narrowed his eyes in alarm. Their sense of smell must be keen as a hound's! He could see the males leaping down the cliffs, brandishing clubs. It reminded him of a disturbed colony of baboons he'd seen once. Gad, but he'd stirred up a hornet's nest! He began to back warily from the river bank. * * * * * There was a grunt behind him; a branch snapped. He tried to whirl around, bringing up his carbine. A pair of arms wrapped around him, seized him in a crushing grip! Shock closed Jupiter's throat. He twisted, wrenched frantically. The arms tightened like steel cables. There were more grunts, triumphant shouts, the crashing of underbrush. Across the river the caveman had come to a halt. Then suddenly he saw them turn and flee, scampering up the cliffs like terrified monkeys, tearing at each other in their efforts to get away from the thing that had him in its grip. Jupiter Jones was a powerful man--doubly so on this planet of mild gravity. Furthermore he'd been in too many tight scrapes to be overly bothered with scruples.