Marie Suzanne Simonin (Pauline Etienne, 2 AUTUMNS, 3 WINTERS), the youngest daughter of an accountant (Gilles Cohen, A PROPHET) is guilted into taking the veil by her parents who have financially ruined themselves arranging the marriages of her older sisters and supporting them even after they have been married off and had children (while still living in relative comfort). Although the austere life of the convent suits Suzanne, she knows in her heart that she has another calling in the world, refusing her vows at the last moment and is returned home. She confines herself to her bedroom until the family priest (Marc Barbé, LA VIE EN ROSE) reveals that the reason she is treated differently from her sisters is because she is the illegitimate product of an affair by her mother (Martina Gedeck, THE LIVES OF OTHERS) and that there is little chance of her marrying well and no chance of a dowry with her sisters' needs to take into account. Her mother asks that she make no claims on her estate after she is gone rather than disinherit her and reveal the scandal, and Suzanne reluctantly takes the veil. When the liberal mother superior de Moni (Françoise Lebrun, THE DIVING BELL AND THE BUTTERFLY - whose art was "hiding all the thorns of religious life" in a "subtle course of seduction" that lead Suzanne to believe that she really was not surrendering anything in her heart by taking the veil - is murdered by the mad Sister Benedictine (Garance Clavel), however, she is replaced by the cold and strict Mother Superior Sister Christine (Louise Bourgoin, BLACK HEAVEN). Suzanne's defiance of new Mother Superior's rule ostracizes her from the other sisters, and the punishments escalate from bullying to starvation and torture. Suzanne pens a memoir and entrusts it to her sole remaining friend Sister Ursule (Alice de Lencquesaing, SUMMER HOURS) whose mother forwards it to lawyer Morante (Fabrizio Rongione, THE KID WITH A BIKE) to work towards annulling her vows. While the church refuses to annul her vows, Morante is able to get her transferred to a more liberal convent; however, the Mother Superior Sister Saint-Eutrope (Isabelle Huppert, ABUSE OF WEAKNESS) harbors an inappropriate form of love for her charges, and the "fits of passion" she experiences for Suzanne may drive jealous Sister Thérèse (Agathe Bonitzer, daughter of Rivette's collaborator Pascal Bonitzer and IF YOU DON'T, I WILL director Sophie Fillières) over the deep end.

Based on the novel by Denis Diderot - which has loosely inspired a number of Italian nunsploitation films as well as a more direct adaptation by Jacques Rivette in 1969 - THE NUN was originally conceived as a practical joke by Diderot and his cronies to lure the popular Marquis de Croismare back to Paris after a business trip in Normandy that ended up as an eight year stay. The joke went awry with the Marquis offering the fictional heroine asylum. Diderot would end up reworking the text into a fictional work of social commentary. The Marquis de Croismare exists here within the story, but as a young man (Pierre Nisse, THE SON) whose ailing father the Baron de Lasson (Lou Castel, FISTS IN THE POCKET leaves for his discovery Suzanne's memoirs. At this point, it almost seems as though Diderot's ruse will come into play in the framing part of the film at the risk of trivializing the film's well-wrought drama. Without such a device, however, this gorgeously-shot (by Bruno Dumont favorite Yves Cape, who also shot Claire Denis' WHITE MATERIAL) and sensitively-acted adaptation seems like mere festival fodder.