On a sunny morning in June, Margaret Carpenter wakes up to find a new iPhone on her doorstep. She switches it on to find a text from her best friend, Charity Atwater. The problem is, Charity’s been missing for over a month. Most people in town, even the police, think she’s dead. Margaret and Charity have been lifelong friends. They share everything, know the most intimate details about one another, except for the destructive secret hidden from them both. A secret that will trigger a chain of events ending in tragedy, bloodshed, and death. And now Charity wants Margaret to know her story, the real story. In a narrative that takes place over one feverish day, Margaret follows a series of increasingly disquieting breadcrumbs as she forges deeper into the mystery of her best friend, a person she never truly knew at all.