Frightmare(1974)

In 1957, Dorothy and Edmund Yates were committed to an institution for the criminally insane, she for acts of murder and cannibalism and he for covering up her crimes. Fifteen years later, they are pronounced fit for society and released. However, in Dorothy's case the doctors may have jumped the gun a bit. Edmund and eldest daughter, Jackie, try to discover just how far Mother's bloodlust has taken her. Meanwhile, youngest daughter Debbie begins to explore the crazy roots of her family tree as fully as possible.