"The human, Goat, for reasons that are not known, stole some of our charts and two of the pregnant female humans, and continued his work at this place to which we are going. But he thought he was still attempting to change the physiology so that oxygen could be stored, and therefore his experiments went wrongly." "But he had your charts," objected Maya. "Even though he was not making the alterations he thought he was, how could he go wrong if he followed the charts?" "The charts showed the changes to be made in the embryonic cells, but they could not show the method whereby the changes are made," replied Qril. "The human, Goat, attempted to make these changes by mechanical, surgical methods but these are too crude to be successful. The method we utilize to make such changes, which is the only right method, is to focus the mental forces upon the embryo. I believe you would call it psychokinesis." Maya was vastly excited at this revelation. "Then Goat's oldest experiments, the ones he called Brute and Adam, were actually the ones on whom you children of the past had performed the embryonic changes!" she exclaimed. "They must have been the sons of the pregnant women he kidnapped. That's why they were more successful than the others!" "That is true," said Qril. "We had completed the change on only one of the two, therefore only that one would develop into an adult who could live in complete independence of air and food, if necessary. The other one would never be able to do it for more than a short period without returning to terrestrial conditions." The party now came over a long low ridge, and the mass of Ultra Vires rose from the desert ahead of them. The sun was near setting, and the black walls of the stronghold huddled sullenly under its crimson rays. The Martians left them here, and Nuwell and Maya went on alone toward their goal. Nuwell expelled an audible sigh of relief. "I'm glad we're free of those monsters," he said. "I don't understand how you could carry on a conversation with such creatures, Maya. It sounded like a series of animal grunts and cries to me. I caught an occasional word, like 'oxygen' and 'psychokinesis.' What were you talking about?" "He was telling me about Goat Hennessey's experiments, and how they differed from the rebels' experiments before Goat came to Ultra Vires," answered Maya. "That kind of talk serves no good purpose," said Nuwell irritably. "The rebel movement has been broken now, and there's no point in thinking about the illegal things they tried to do." They came down the slope and approached the southern airlock of Ultra Vires. The airlock was still sealed. Nuwell activated it, and they went through it into the big building. It was dark inside. Nuwell fumbled around a wall and found a light switch. He pressed it, but nothing happened. "The electrical system isn't operating," he said. "We'll have to use our marsuit torches."