The action takes place in St. Petersburg, at the beginning of the 20th century. After a ten-year absence, the Ural millionaire, philanthropist and “Russian Casanova” Andrei Yakovlevich Revizanov returns here, with whom more than one woman’s fate is connected. Under unclear circumstances, Revizanov is killed at his home. Investigator Sinev finds a blue envelope and thus gets his hands on evidence indicating a murder, but the solution to the mysterious murder does not come immediately...