In Edwardian England, Violet has a fairy tale existence: loving husband, beautiful baby son and luxurious home.
She wants for nothing. But soon after the birth of her baby the idyll begins to disintegrate.
Violet becomes obsessed by a book of fairy tales her husband has locked away in a safe.
Paranoid hallucinations begin to haunt her and she starts to question her sanity.
Meanwhile, vulnerable young women are starting to disappear from the nearby asylum.
Soon Violet herself is interned in the asylum for treatment only to discover, on coming out, that her husband has hired a nanny while she has been away, the beautiful, enigmatic Clara.
The brutality of the asylum is nothing compared to the horrors that now lie in wait.