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...

Henry Crossley is an artist whose wife is spending a week's holiday with her aunt. But when her aunt comes to see him, worried because her niece has not arrived, a police investigation into her disappearance begins. It seems that Henry was fully occupied at the time his wife went missing; but is his alibi completely truthful?

Special investigator Duke Martin is in London to investigate the authenticity of a rare postage stamp called the Barbados Overplate. Someone is willing to commit murder to get his or her hands on the stamp, which puts a crimp in Duke's efforts to romance every beautiful woman he meets.

An American is visiting Britain and finds himself in possession of a briefcase full of secret documents that the spies of many different countries seem determined to get.