After a long wartime separation, pianist Christine Radcliffe is reunited in New York with her fiancé, cellist Karel Novak. Although Christine excitedly plans their wedding, she is reticent about her past. When Karel demands to know how a struggling musician like Christine can afford an elegant apartment and expensive wardrobe, Christine explains that she has taken on students, something they long ago agreed they would never do, and was ashamed to tell him. The next morning, Christine receives a call from composer Alexander Hollenius, whose mistress she has been, and announces her coming marriage. Later, Hollenius arrives unexpectedly at a party celebrating the marriage, and tells Karel that he fears marriage will interfere with Christine's devotion to her music. Karel is convinced that Hollenius' strange behavior is due to jealousy, especially after Hollenius discloses that Christine never had students. The following day, Christine visits Hollenius and begs him not to reveal their relationship because she is afraid that the information would strain the temperamental Karel's nerves. Later, Karel visits Hollenius, believing that Christine will be there despite her assertion that Hollenius was never more than her teacher. To his surprise, he discovers that Hollenius is listening to a recording that Karel made before the war. Hollenius is impressed by Karel's talent and offers him a new cello concerto that he has written. When Christine hears Karel practicing Hollenius' concerto, she becomes convinced that Hollenius intends to use the concerto to destroy Karel. Her fears are intensified when Karel returns home after playing the concerto for Hollenius and rails against the composer's dictatorial behavior. When Christine reveals her apprehensions to Karel, he demands to know why she is afraid that Hollenius will take the concerto away from him, but Christine still refuses to tell her husband the truth about her relationship with the composer. The next day, Christine returns to Hollenius' apartment to beg him not to take out his anger on Karel, and Hollenius scoffs at her, responding that his first duty is to his music and that he is sure Karel will perform the piece well. He urges Christine to tell her husband the truth. As she leaves the apartment, Christine sees Bertram Gribble, the orchestra's first cellist, waiting in the foyer and is sure that Hollenius intends to replace Karel with Gribble. On the night of the performance, after Karel has left for the concert hall, Christine again visits Hollenius and begs him to promise that he will not tell Karel of their relationship, and when Hollenius refuses, Christine shoots him. She then tries to make the murder look like a suicide and leaves for the concert. Karel performs the music brilliantly, and the way now seems clear for a successful concert career in America. When Karel and Christine are alone in his dressing room, however, she realizes that Hollenius always intended for Karel to perform his composition. She then confesses the murder to Karel as well as the truth about her relationship with Hollenius. Karel asks her to keep the murder a secret, but Christine is finally tired of her deception, and the couple leaves for the police station, walking past crowds of Karel's admirers.