The doctor was sure: this girl, who introduced herself as Ariadna, was an ordinary madwoman. She read the first part of the historical novel by his mentee, the famous writer Derzhavin-Kleopatrov, about the return of Jack the Ripper, and she was visited by a vision of a murder committed by a follower of the famous criminal in our days. But it soon became clear that Ariadne was not deceiving: the murder happened and was arranged exactly as she described! The unknown person copied fictitious events from a novel published in parts, and the identity of a maniac from a fictional universe could become the key to solving a crime in the present. But Derzhavin-Cleopatrov stubbornly hid who the killer would be in his book...