A convicted female blackmailer is found murdered in her flat and suspicion falls on three men, all of whom the police believe may have had reason to wish her dead

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.

In this contemporary update of Frank H. Spearman's Western hero, Whispering Smith is now a sleuth who arrives in London on holiday, but is soon called in to solve the case of a suicide which the father of the deceased woman thinks was murder.