In Moscow, a famous dentist was killed - Yakov Gorobetsky. The corpse is discovered by the son of the murdered man - Vitaly. The results of the work of experts lead to a consequence of an unexpected discovery. Vitaly is not Gorobetsky's own son. His real father - Bakhtemyev - led a major criminal group in St. Petersburg, he was arrested and shot in the early eighties. Mother Vitaly married Gorobetsky, who adopted the boy. During the investigation, Kamenskaya finds out that the mother of Bakhtemyev the elder has been killed in Petersburg. The alleged killer was detained, but he managed to escape. Kamenskaya is going to Petersburg.