 Based on the information in the text, why would Don choose to leave Superior?
Radio messages stated simply that Superior had seceded from Earth. But Don Cort, stranded on that rising town, was beginning to suspect that nothing was simple about Superior except its citizens. The state police converged on the former site of Superior from several directions. The train's schedule called for it to pass through but not stop at Superior at 11:58. A National Guard officer volunteered to take a jeep down into the pit, having found a spot that seemed navigable. The object loomed out of a cloudbank at twelve thousand feet and Studley changed course to avoid it. A few minutes later he had relayed a message from Superior, formerly of Ohio, addressed to whom it might concern: It said that Superior had seceded from Earth. One other radio message came from Superior, now airborne, on that first day. Don Cort had been dozing in what passed for the club car on the Buckeye Cannonball when the train braked to a stop. If the girl had given Don Cort more than that one glance, or if it had been a trained, all-encompassing glance, she would have seen a man in his mid-twenties—about her age—lean, tall and straight-shouldered, with once-blond hair now verging on dark brown, a face neither handsome nor ugly, and a habit of drawing the inside of his left cheek between his teeth and nibbling at it thoughtfully. Don hesitated, shrugged at the redhead, said, "Excuse me," and followed the conductor. Don made his way up to the locomotive and found a bigger knot of people gathered in front of the cowcatcher. Don saw two men who must have been the engineer and the fireman talking to an old bearded gentleman wearing a civil defense helmet, a topcoat and riding boots. Don Cort and the fireman walked cautiously toward the edge while the professor ambled ahead with the familiarity of one who had been there before. Nevertheless, Don could see that it apparently was a neat, sharp edge, not one of your old ragged, random edges such as might have been caused by an explosion. He didn't have to stand on tiptoe any more than he had to sit on the edge of his seat during the exciting part of a movie, but the situation seemed to call for it. Don looked at the fireman, who had an unbelieving expression on his face, then at the bearded old man, who was smiling and nodding. "If what Mr. Cort and the fireman say is true. Well, Professor Garet telephoned and said, 'Hector'—that's my name,
 He had to deliver the handcuffed briefcase.
 He had to deliver the handcuffed briefcase.  He had a family to return to that would be expecting him at home.  He feared the future of Superior.  His wife would not appreciate him spending time with Alis.