In a state correctional institute for teenage girls, Madame Appel, the superintendent, rules with an iron fist. The State appoints thirty-year-old Yvonne to evaluate the situation. The young woman is convinced that the girls should feel wanted rather than be constantly subdued and is accordingly determined to make Madame Appel change her methods of education. On a private level Yvonne is secretly engaged to Guy Maréchal, the doctor serving the institute. Unfortunately for her, the latter starts flirting with Nelly, a beautiful but rebellious inmate. Another prisoner, Renée, who has discovered the romance, blackmails Nelly...