Caught in a loveless marriage, Dr. John Winnington (Ronald Howard) can't stop himself from falling for his wife's (Mary Laura Wood) younger sister, Christine (Olga Edwardes). But when he suddenly becomes the prime suspect in his wife's tragic murder, John relies on his friend Eric (John Bentley) to clear his name. This classic murder mystery encourages viewers to evaluate all of the clues and guess the killer's identity.