A noted expatriate filmmaker's hard work to reestablish himself in Britain is nearly undone when a woman who claims to be his one-time mistress begins writing him threatening letters. This sudden revelation threatens not only his marriage but also his career. It doesn't help that the director doesn't know the blackmailer's identity. He finds out that her letters are coming from Newcastle, and so he and his wife head off to learn the truth. They meet her and his wife is so convinced that she leaves. Unfortunately, the director still doesn't recognize this woman who seems to have such intimate knowledge of him, and he begins to question his own sanity. The rest of the mystery centers on his attempts to learn the truth about the woman and her true motives.