 How does Sattell hope to get rid of Pop?
There is nothing like it on Earth, of course. 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. Even now there were some who had to be carried, but there were some tougher ones who were able to walk to the rocketship if Pop put a tarpaulin over their heads so they didn't have to see the sky. Sattell got the shakes when he thought of Pop, and Pop rather probably knew it. Pop had come back to consciousness in a hospital with a great wound in his head and no memory of anything that had happened before that moment. 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. 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. With freight costing what it did, fuel and air and food came frozen solid, in containers barely thicker than foil. 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. 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. The sun rose very, very slowly in what by convention was called the east. He wrote with the desperate, impassioned, frantic blend of persuasion and information and genius-like invention of a prisoner in a high-security prison, trying to induce someone to help him escape. But then an event occurred which bore directly upon Pop Young and Sattell and Pop Young's missing years. It didn't seem to have anything to do with Pop or with Sattell.
 Escaping on board a secondhand lunar tour vessel
 Luring him down into the Big Crack and killing him  Hiring an assassin from a neighboring planet  Blowing up the shack near the edge of the Big Crack  Escaping on board a secondhand lunar tour vessel