Director Luis de la Madrid's Spanish horror has a ghostly nun exacting bloody vengeance on those responsible for her death. The head of a Catholic school in Barcelona, Sister Ursula (Cristina Piaget) has relentlessly bullied and abused her students. When a 15-year-old pupil is found to be pregnant, she attempts to 'cleanse' the girl by immersing her in water but is accidentally killed by the girl's five classmates who are trying to stop the ceremony. 20 years later the school is newly reopened and two of the original classmates are found dead, prompting those still alive to face their worst fears. With the now teenaged daughter of the original pupil in tow, the remaining friends set out to end their nightmare once and for all.