The last summer of childhood.

The film takes place in Moscow in 1925, during the New Economic Policy (NEP). The three main characters - Misha, Genka, and Slava - have grown up and become Komsomol members. A murder occurs in their courtyard: engineer Zimin is shot dead at night. The prime suspect turns out to be a local hooligan. But Misha refuses to believe him completely and tries to find evidence on his own.