And So Died Riabouchinska (1956)

A dead man is found in the basement of a theater, and a detective comes to investigate. He learn that the deceased had been seen near the theater asking for Fabian, the ventriloquist. As the detective questions Fabian in his dressing room, a voice comes from the box in which Fabian's female dummy is stored. When the dummy, Riabouchinska, continues to talk, the detective is annoyed, thinking that the ventriloquist is trying to be funny. But the detective humors him and 'talks' to the dummy, and he soon learns about a web of tensions involving Fabian, his wife, and his manager. Much of the tension concerns the dummy - and there is also a connection with the dead man.