The two Earth-people stared around them curiously. They were bathed in a bright light, and yet there was no apparent source of illumination. It began to dawn on them that the rocks which formed the side walls at the base of the shaft, were themselves luminous, glowing with a curious greenish light. Dynamon tilted his head back and stared up into the darkening shaft. Suddenly, he uttered an exclamation and, seizing Keltry by the wrist dragged her to one side. A few seconds later, a round object dropped out of the shaft and bounced on the ground. It was Keltry's counter-gravity helmet. Dynamon reached down and picked it up. "It's a good thing that these things are well built," he remarked with a smile, "or this would be smashed to bits. The knob is still set for plus ten pounds, and that was quite a fall. I wonder whether it still works." He twisted the knob experimentally and the helmet started to sail upward. "Say!" Dynamon cried. "It works, all right! Here, put it on Keltry." Keltry accepted the helmet with a laugh, put it on her head and was buckling it under her chin when her blood suddenly congealed in her veins. A loud shout rang echoingly through the shaft. Dynamon whirled around and beheld a curious figure standing in front of a rock not sixty feet away. It stood upright on two legs, and cradled a sort of club in its arms. Its head was covered with long, yellow hair that fell down on to its shoulders, and the lower half of its face was covered with coarse, yellow hair. Blue eyes glinted from under shaggy brows in a menacing glare at the two Earth-people. "It looks quite human, doesn't it?" whispered Keltry. Dynamon nodded and slid his ear phone off his right ear as he saw the stranger's hairy mouth opening and closing. Keltry followed his example in time to hear the stranger's rumbling voice. "Whoo-yoo?" Dynamon touched Keltry's hand. "That sounded like 'who are you' didn't it?" he said wonderingly. "It certainly did," Keltry answered. "I think that's some kind of human." "If it's a human," Dynamon said, "then there must be some sort of breathable atmosphere down here. You notice he's not wearing any oxygen mask." "Whoo-yoo?" the stranger repeated, "an whey cum fum?" "He's speaking a kind of English!" said Keltry excitedly. "He said, 'who are you' and 'where do you come from'!" "By Jupiter!" cried Dynamon. "I think you're right. If he can breathe without a mask, so can we. I'll have a little talk with him." A moment later the centurion stood bare-headed, helmet and oxygen mask in hand. "We're humans from Earth," he told the stranger, pronouncing each word carefully. "Who are you?" The stranger's eyes and mouth flew open in astonishment and the rod sagged in his hands. "Humes! Fum Earth!" he cried hoarsely, then turned his head, and gave an ear-splitting yell. * * * * *