Jilted thriller writer Lady Violet Thorn has withdrawn to the Suffolk market town of Montford with two servants and her leading character, the adventuress Ruby Gibson, for company. Violet's peace is disturbed when a stranger asks her for help, claiming that a friend is being kept prisoner in her own home. Her visitor seems so afraid that Violet, despite her scepticism, is persuaded to investigate. A woman is killed outside Violet's house, then another murdered in the town and as the deaths mount up, she becomes convinced that they all lead to one place: the increasingly forbidding Haglin House, and whoever lives there.