Mr. Ueno, retired, lives alone; he talks to Maria, a maid-droid his parents brought from their factory decades ago. Maria became Ueno's companion after his parents' deaths, and now her battery is run down; there are no replacement parts. Meanwhile, Inspector Akagi and her police squad are looking for a serial rapist that may not be human; however, if it's a robot, in harming people it would be disobeying Asimov's rules of robotics. Akagi's inquiry takes her to a droid factory run by Mr. X; he helps by explaining why host-droids, the male equivalent of a maid-droid, don't sell. What will Ueno and Akagi learn about love and the nature of men and women?