Love Letters of a Portuguese Nun (1977)

One of Jess Franco’s finest films this tells the story of 16 year old Maria (Susan Hemingway) who is forced to enter into a cloister because Father Victor (William Berger) catches her fooling around with her boyfriend and forces her mother to give her up or the child will be condemned to hell. While in the cloister, Maria is forced to demonstrate her obedience by performing self-demeaning acts and is tortured and beaten….all to the delight of Father Victor and the Mother Superior. She begins to realize that the nuns give themselves to the Devil in unrestrained satanic orgies. In desperation Maria writes a love letter to God and throws it out the window of her cell.