A beautiful, vivacious, outgoing, bohemian Sarah (Lou de Laâge) turns up as a new student in the final year high school class of the quiet, introvert, pensive, passive and always melancholic Charlie ( Joséphine Japy) whose parents are undergoing a divorce and is arranged by the teacher to sit next to Charlie. Sarah introduces herself as the daughter of a mother who is working for an NGOin Nigeria, street-wise about many things in the larger world, with some interesting sex with an English boy and now living with an impossible aunt. Very quickly, they turned into the the best of friends, with Sarah starting out at first asking if she could come to Charlie's house to do revisions because she couldn't put up with her aunt with whom she was then living and gradually actually living in Charlie's house, sharing her bed in a middle class home( where Charlie lives alone with Vanessa (Isabelle Carré ) her mother being deserted by Charlie's father Sasha (Radivoje Bukvic)) and much else including her interests, her leisure, her friends and her sensitive feelings. Sarah takes Charlie to parties where they tell jokes, take walks together, go to beaches, share stories, drink with other high school kids, smoke not only cigarettes but hash and generally do the kinds of things teenagers do. Charlie never felt so happy.
But the good times were not to last very long. Eventually they fell out with each other as Charlie found that Sarah was a compulsive liar and has not the slightest hesitation in taking over a boy who has a liking for Charlie at the camping house Vanessa took them to for a vacation, the affection of Charlie's mother and that Sarah was in fact living in a prefabricated container-like house in a slum with an alcoholic mother in dirty clothes who turned the tiny rooms literally into a rubbish dump. When in a momentary outburst of anger, Charlie overheard Sarah gossiping about her most intimate secret which she confided to Sarah viz that she never went through her first sexual experience, Charlie could not resist telling her friends that Sarah never went to Africa. Thereafter Sarah never spoke to Charlie again and began writing insulting remarks about Charlie on the walls of the student lockers, her desk etc and acted as if Charlie were transparent.
Close to the end of the film, when Sarah sustained an attack on her face by one of her flings and turned up at Charlie's door late one night telling Charlie that she was only person in the world to whom she could turn to for help, Charlie nursed her with the greatest care but the following morning once they approached school, Sarah told Charlies that she did not want to be seen with Charlie together in front of the other students. When the film ends, Sarah was in Charlie's room, telling her that she would be moving to Paris and for such purpose wanted to pick up all her belongings she left at Charlie's house. When she remarked sarcastically that she would henceforth leave Charlie to her little home in a little provincial town, with her little ambitions, and boring and uneventful little life, Charlie, who herself has a mild form of asthma, could take it no longer and stifled her with a pillow.
It's a film which sensitively captures all those kinds of details in the school and off campus life of a female teenager student, the lesbian-ish feelings which Charlie harbors towards Sarah, the petty bitchiness that school girls are capable of, largely through the eyes Charlies and by implication that of Mélanie Laurent, thanks to the excellent cinematography of Arnaud Potier and thanks also to the excellent performances of the two protagonists Lou de Laâge and Joséphine Japy which renders believable the kind of the petty affections, rivalries, jealousies and unexpected fatal outburst in the lives of certain teenage girls otherwise banal growing up story of how intensity of intimacy between teenage girls having its roots in domestic unhappiness of two dysfunctional contemporary families could easily turn into a source of mutual destruction with literally "fatal" consequences. At the close of the film, we find Charlies gasping for breath as she stands in front of the window of her house staring blanking at us, when we hear Vanessa let out an off screen cry of horror at her discovery upstairs. I could not help feeling if somehow, some of the sequences might not be shortened but perhaps that's Mélanie Laurent way of telling her story, slowly, sensitively, and subtly.