 What is the relationship between Sattell and Pop Young?
His name was Sattell and he had reason not to talk. Pop Young alone knew the whole truth, and he kept his mouth shut, too. Pop lived in it all alone, and in his spare time he worked industriously at recovering some missing portions of his life that Sattell had managed to take away from him. Sattell got the shakes when he thought of Pop, and Pop rather probably knew it. He met Sattell quite by accident. All of which happened back on Earth and a long time ago. At such times Pop hardly thought of Sattell. He'd started to follow Sattell knowing what had happened to his wife and children, but it was hearsay only. When Sattell fled to another continent, Pop followed because he had some distinct memories of his wife—and the way he'd felt about her—and some fugitive mental images of his children. When Sattell frenziedly tried to deny knowledge of the murder in Tangier, Pop had come to remember both his children and some of the happiness of his married life. Even when Sattell—whimpering—signed up for Lunar City, Pop tracked him. If so, Sattell had profited by less than two days' pay for wiping out everything that Pop possessed. Sometimes, in the shack on the far side of the Moon, Pop Young had odd fancies about Sattell. The sun rose very, very slowly in what by convention was called the east. Near Sattell, he found memories of times when he was a young man with a young wife who loved him extravagantly.
 Sattell is trying to escape Pop, who believes he killed his family
 Sattell uses methods to help Pop recover his memories  Sattell is trying to escape Pop, who believes he killed his family  Sattell was Pop's neighbor back on Earth  Sattell is Pop's son and the only witness who saw Pop murder his wife and other children