Dr Péter Gergely, assistant professor at the University of Budapest, and his wife Mária celebrate their wedding anniversary. They are listening to Tchaikovsky's Symphony No. VI when he is called in sick. Left alone, she goes to an address given by an unknown caller, where she finds her husband in the arms of a strange woman. She does not believe in her husband's innocence, divorces him and marries the lawyer Dr. Tibor Máté, who has been besieging her for years. In despair, Peter attempts suicide, and the unknown girl who caused the tragedy appears at his bedside. The journalist István Bálint discovers that the girl was paid off by Dr. Máté and unmasks the instigator. Peter recovers, but the excitement causes him to lose his memory. Mary and the doctor reminisce about their wedding anniversary. The experiment succeeds, he remembers everything, and they resume their life together where they left off: listening to Tchaikovsky's symphony.
