After an unexpected split from her fiancé leaves her distraught, Grace Crawford retreats to her sister Catherine’s secluded residence for solace. She soon discovers that Catherine is grappling with paranoid schizophrenia, a condition that also afflicted their deceased mother, who died by suicide. As Grace processes this difficult truth, she stumbles upon another disturbing secret that threatens her mental stability, forcing her to fight to protect herself and her family from additional danger.