England, late 1800s: Henrietta Marsh has felt a shadow following her for most of her life. There are whispers among her colleagues that this darkness led to the violent death of her parents. When she is incarcerated in a mental hospital, she charts the events that led her there. Meanwhile, her only friend, and the man she loves, fight to save her. But can Henrietta be trusted, or is she truly mad - and guilty of the heinous crimes of which she is suspected?