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?