Angry and upset after a sudden breakup with her fiancé, Grace Crawford seeks sanctuary at the remote home of her sister, Catherine. It becomes clear that Catherine is suffering from paranoid schizophrenia, much like their late mother, who had taken her own life. While coming to terms with this heavy realization, Grace also uncovers another terrible little secret that has her struggling to maintain her own sanity and ultimately scurrying to save herself and her family from further harm.