In 19th-century France, teenage Teresa Garan is the daughter of a cabaret-singer single mother. A friend of her mother pays for her to have one year at Ms. Fourneau's boarding school. Soon Teresa learns that the school is also a prison: Ms. Fourneau keeps everything locked up. Her protégée, the wicked student Irene Tupan, keeps watch over the other girls and uses her power to bully and torture them. Ms. Fourneau's teenage son is a peeping Tom and his mother keeps him secluded from the girls, saying they're worthless and he needs to find a girl who's more "like his mother." When students start vanishing, their classmates think they're running away, but they're actually being abducted and murdered by a serial killer. When Irene discovers that Teresa is secretly meeting Luis, she tortures her until Teresa decides to flee in the middle of the night. What will happen to her?