On the eve of his wedding, a young doctor leaves Moscow to see his mother who lives in a nature reserve. Things are complicated by the fact that the doctor's ex-girlfriend is also there, and she is expecting a child.

A group of old friends have a tradition of going to a public bathing house on New Year's Eve. Occasionally too much vodka and beer makes two of them unconscious. The problem is that one of them (Sasha) has to go to Leningrad but another one (Zhenya) goes. Zhenya wakes up at Leningrad airport. Believing that he is still in Moscow he takes a taxi and goes home. The street name, building and even apartment number, the way an apartment complex looks the same and the key coincide completely - just typical Soviet-type 'economy' architecture. Imagine the surprise of Nadya when she enters her apartment and finds a man without trousers in her bed. What's more - Nadya's fiancé also finds him there...