Bedelia Carrington is living happily, it appears, in Monte Carlo with her husband Charlie Carrington. But a cultivated young artist, Ben Chaney, begins probing into her past with curious concern. Chaney, who is really a detective, learns that Bedelia's obsession for money has led her, in the past, to husband-poisoning for the insurance money.

An elderly lady manages to sneak some pills away from her nurse and dies of an overdose. The nurse is tried for murder and acquitted. Some time later the nurse, under a new name and identity, cares for a patient who also dies of an overdose. When her real identity comes out, suspicions arise.

When his best friend is murdered inside a London dancehall, a cab driver and his girlfriend involve themselves in the investigation and discover a major criminal operation hiding behind the club's friendly facade.