30s. Leningrad. Young provincial Nikita Fedotov, having failed to enter the conservatory, rushes into the Neva in despair, but policeman Koshkin, a witness to the incident, pulls him out and invites him to work for the criminal investigation department... Nikita accepts the offer.
Soon he gets the opportunity to sing not only on the phone for his cute neighbor Zoya, but also to act as a professional touring singer, and at the same time monitor the work of an international gang of diamond thieves...
