During the winter of 1943-44, Julien Quentin, a student returning to his Carmelite boarding school in occupied France, attempts to project a tough demeanor to his peers. However, beneath this façade lies a deeply pampered boy who longs for his mother’s presence. As he settles back into the mundane routine of school life, things take an unexpected turn with the arrival of three new students. One of them is Jean Bonnet, who shares Julien’s age. Initially, Julien and his classmates look down on Jean, who struggles socially but possesses remarkable talent in mathematics and piano.
One night, Julien awakens to find Jean wearing a kippah, engaged in Hebrew prayers. Driven by curiosity, Julien explores Jean's locker and uncovers his true identity—Kippelstein. This revelation comes alongside learning that Père Jean, the headmaster played by François Berléand, has heroically chosen to offer secret sanctuary to hunted Jews.
After a playful treasure hunt, a friendship blossoms between Julien and Jean. The bond strengthens when Julien, during a visit from his mother, invites Jean to join them for lunch at a fancy restaurant since Jean’s own parents could not attend. The atmosphere at the table shifts dramatically when Julien’s father is discussed. Upon hearing Julien’s brother question their father’s allegiance to Marshal Pétain, Madame Quentin insists, “No one is anymore.” The meal takes a distressing turn when the Milice arrive, attempting to expel a Jewish diner. In a moment of defiance, Julien’s brother refers to them as "Collabos," inciting the wrath of the Milice commander, who retorts, “We serve France, madam. He insulted us.” When a Wehrmacht officer orders the Milice to leave, they comply, albeit begrudgingly. Madame Quentin remarks on the dignity of the Jewish diner, expressing her neutrality towards Jews but revealing her disdain for socialist politician Léon Blum.
Troubles arise when Joseph, the school’s assistant cook, is caught selling food supplies on the black market. He implicates several students, including Julien and his brother, François. Despite his anguish over the injustice, Père Jean chooses not to expel the students, concerned about the ramifications for their affluent families.
As January 1944 arrives with an icy chill, a Gestapo raid targets the school in search of Jean Kippelstein. In a moment of unintended betrayal, Julien inadvertently reveals Jean’s location. While chaos ensues as the Jewish boys are hunted, Julien confronts Joseph, who justifies his act of treachery by saying, “Don’t act so pious. There’s a war going on, kid.” Julien, filled with disgust, hastily departs. He and Jean engage in their habitual book exchange as they prepare to leave, marking a poignant farewell amidst the school’s closure.
When the students are gathered in the courtyard, a Gestapo officer denounces Père Jean's noble deeds, labeling the French as weak. A heart-wrenching farewell unfolds as Père Jean, trailed by the Jewish boys, is escorted away. As he passes through the students, they call out, “Au revoir, mon père!” He stops, turns slightly, and with a reassuring voice responds, “Au revoir, les enfants! À bientôt!” Jean is the final one to exit through the garden’s metal gate, offering Julien a brief, wistful glance, which Julien shyly acknowledges with a wave.
The film concludes with an older Julien reflecting on the events of that fateful January morning. He shares the somber reality that Bonnet, Negus, and Dupre perished in Auschwitz, while Père Jean met his fate at Mauthausen. Although over 40 years have passed, Julien asserts that those haunting memories will remain engraved in his mind until the end of his days.
