 What effect does Sattell's proximity have on Pop?
His name was Sattell and he had reason not to talk. The shack and the job he filled were located in the medieval notion of the physical appearance of hell. There is nothing like it on Earth, of course. When it was first found, scientists descended into it to examine the exposed rock-strata and learn the history of the Moon before its craters were made. 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. There were air-tight bulkheads for safety, and a hydroponic garden to keep the air fresh, and all sorts of things to make life possible for men under if not on the Moon. In the Moon's slight gravity, a man is really adjusted to existence when he has a well-developed case of agoraphobia. With such an aid, a man can get into a tiny, coffinlike cubbyhole, and feel solidity above and below and around him, and happily tell himself that it feels delicious. It doesn't take too long for the low gravity to tear a man's nerves to shreds. Sattell got the shakes when he thought of Pop, and Pop rather probably knew it. And Sattell turned gray and frantically denied that he'd ever seen Pop before. All of which happened back on Earth and a long time ago. It seemed to Pop that the sight of Sattell had brought back some vague and cloudy memories. The pilot killed all forward motion just above the field and came steadily and smoothly down to land between the silvery triangles that marked the landing place. While they stayed at space-shadow temperature, the foil would hold anything. And a cover of insulating moondust with vacuum between the grains kept even air frozen solid, though in sunlight. 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.
 It restores Pop's memories of his wife and children
 It brings Pop's memory of the murder of his family into clarity  It motivates him to plot his revenge against his family's murderer  It amplifies the pain of his Pop's head injury  It restores Pop's memories of his wife and children