Set in Spain in 1974, the film follows Ana, a 19-year-old from Barcelona considered rebellious by her wealthy family, who is set by her father to a reform institution run by the Patronato. There, she endures a strict discipline regime imposed by nuns, especially the merciless Sister Socorro. Amid the harsh conditions, she finds solace in a deep bond with another girl, Sole. Together, they struggle to survive and attempt to escape, though fate cruelly reunites them when Sole is recaptured. Determined to protect her friend, Ana confronts Sister Socorro's twisted authority and is forces to make a final, painful sacrifice in an attempt to save them both.