1918 Odessa. German occupiers plunder the city. Sailor Petrus, who has lagged behind the Red Army detachment, saves one of the victims of bandit terror - the girl Marusya... Years have passed. The time has come for peaceful construction in the country. Red commander Petrus and Marusya, who has become a teacher, meet in Moscow in one of the cafes, where both were attracted by the sounds of the popular song “Eh, apple...”, accompanying the adventure of the heroes.