Suzanne, Renee, Nina and Marta all hate being in prison, being slapped and treated badly, and so all the girls are trying to escape. Madame Appel just causes chaos all the time, with her harsh manners. When Yvonne with her free-thinking ways is put in charge of the school for misbehaving girls, and asks them to tell her their complaints, they don't believe her at first. Yvonne is in love and about to marry the establishment's doctor, and it does not help that one teenage girl falls for him - and is corresponded. It's a hard life for the girls, and for the new female warden.
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