The synopsis: Anna returns home from a stay in a psychiatric institution following her mother's accidental death, and soon teams up with her older sister to see if their father's new girlfriend — their mother's former nurse — might be the reason their mom is dead.
The twist: While we're led to believe the new girlfriend is a murderer, it's actually Anna who does all the killing in the film. She inadvertently caused both her mother and sister's deaths — that's right, her older sister isn't actually alive, either — and the memory of it drove her crazy. She ends up murdering the girlfriend, and going back to the mental institution.
The amount of damage it'll do to your psyche: 🔪🔪