A pair of reporters try to discover the link between three unsolved, seemingly isolated murders. The only connection between them is they all took place on the same day in three successive years. The police don't trust their instincts - but as 10th July nears again, a solicitor has started receiving threatening letters...

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.