Set in France, the story follows Denis Leterrand, a precocious 14-year-old boy attending a strict Jesuit boarding school. While performing charity work visiting patients at a local hospital, Denis crosses paths with Sister Clotilde (Sœur Clotilde), a young, beautiful Catholic nun who is roughly twice his age. 

What begins as an innocent fascination rapidly transforms into an overwhelming, mutual infatuation. Sister Clotilde struggles deeply with her faith, her vows, and her inability to define or control her growing feelings for the boy. Despite the massive barriers of religion, society, and age, the two give in to their desires and become secret lovers