David Draper, a fifteen-year-old biochemistry student on Mars, secretly cooks designer drugs for a local dealer named Hutch while navigating the pressures of his senior labs and an upcoming placement. His aunt Bobbie Draper, a former Marine on indefinite leave after the events on Ganymede, has moved in with his family, complicating his ability to work for Hutch. When David's contact Leelee sends him a desperate message asking for money and telling him not to talk to Hutch, David learns that Hutch effectively owns her as property. Determined to buy Leelee's freedom, David cooks an enormous batch of drugs worth far more than his secret savings and confronts Hutch, but the dealer is furious at the market flooding this would cause and pulls a gun. Aunt Bobbie, who had followed David and waited outside, intervenes with decisive military efficiency, disarming Hutch and negotiating Leelee's release along with David's clean break from the operation. The experience helps Bobbie find her purpose again, deciding to return to work, while David goes on to his development placement and a promising career in terraforming research.