In the middle of the night, a phone call rings in one of the city police departments. A stranger reports that he killed two people in a car near a lake and opens an account for the victims. The case is entrusted to the gloomy, strict criminal investigation investigator Viktor Demyanovich Mironov, or simply the Ministry of Internal Affairs, as his colleagues call him behind his back. He is helped by a young forensic expert, Arseny Romanov, who has been fascinated by stories about maniacs since childhood. After a series of murders, it becomes clear that all the crimes were committed with one weapon, which belongs to the new assistant investigator, the son of the head of the department, Alexander...