In 1988, the abusive and deranged Nun Ursula is the principal of a Catholic boarding school in Barcelona. When she finds that the teenage student Mary is pregnant, she decides “to purify” the girl with water, almost killing her. Her class and dorm mates Joanna, Christine, Eulalia, Zoe and Susan fight with the nun and drown her in a bathtub. The six teenagers dump her body in a lake with holy water and make a pact of silence. Eighteen years later, the spirit of the nun is released from the lake and possesses the daughter of Mary, Eve, seeking revenge against the former students and killing each one of them like their saint patrons did to achieve the forgiveness of God through punishment and penitence, pain and sacrifice.