As soon as Kerstin Kvist arrives at remote, ivy-covered Lydstep Old Hall in Essex, she feels like a character in a gothic novel. A young nurse fresh out of school, Kerstin has been hired for a position with the Cosway family, residents of the Hall for generations. She is soon introduced to her "charge" John Cosway, a thirty-nine-year-old man whose strange behavior is vaguely explained by his mother and sisters as part of the madness that runs in the family.

Weeks go by at Lydstep with little to mark the passage of time beyond John's daily walks and the amusingly provincial happenings that engross the Cosway women, and Kerstin occupies her many free hours at the Hall reading or making entries into her diary. Meanwhile, bitter wrangling among Julia Cosway and her four grown daughters becomes increasingly evident. But this is just the most obvious of the tensions that charge the old remote estate, with its sealed rooms full of mystery. Soon Kerstin will find herself in possession of knowledge she will wish she'd never attained, secrets that will propel the occupants of Lydstep Old Hall headlong into sexual obsession, betrayal, and, finally, murder.