Friendships between women have the ambiguous vitality of growing vines: They can either strangle or nurture, and at times it can be hard to tell the difference. That's particularly true for young women first stepping into the puzzling gray area of rivalries and loyalties. How best to support your friends as you also strive to get what you want for yourself? Breathe, Mélanie Laurent's second film as a director (her first was 2011 drama The Adopted), explores the charred-black quadrant of that gray zone, the place where a close friend's betrayal can be so painful it triggers a kind of madness. It's a chilly, elegantly assured little picture, a horror story with its roots not in fantasy but in the reality of hurt feelings. Teenage girls can be ruthless toward one another, but in the end, maybe the people they're most in danger of hurting are themselves.

Charlie (Joséphine Japy) is a retreating but also somewhat petulant 17-year-old growing up in some unnamed provincial French town. She appears to be just going through the motions of school, unsure of who or what she really wants to be and seeming not to care. Her parents (Isabelle Carré and Radivoje Bukvic) are on the verge of splitting up — they're so preoccupied with their own problems that they barely have a minute for her.

Then a newcomer shows up in Charlie's class: Sarah (Lou de Laâge) is brash and dazzling, everything Charlie — a serene, natural beauty — is not. Sarah tells her new classmates that her mother works for an NGO — the two travel around a lot, she explains, as she lights up a cigarette she claims is from Nigeria. (Her audience for this act of rebellion is clean-living French teens who know better than to smoke.) Charlie is drawn to Sarah's cool-girl glamour, and the two become fast friends. Charlie's previous best friend, sweet, loyal Victoire (Roxane Duran), is shut out of the circle, and even the guy Charlie's attracted to, Lucas (Louka Meliava), recedes in the context of this glittering newcomer.

Sarah dresses Charlie up, and the two go out clubbing, embracing and kissing like extremely affectionate sisters. Sarah accompanies Charlie and her mother on a family holiday and, during a bout of playacting, plants an erotic kiss on Charlie's lips — though she's also interested in seducing the young buck with whom Charlie's mother is dallying. It's at this point Charlie realizes that Sarah might be a genuinely threatening presence, though we've cottoned to that fact much earlier: Sarah's sexy pout and honey-blond tousle of curls make it clear she aims to be queen of the jungle, while Charlie — who happens to be asthmatic — is likely to be left gasping in her wake.

Treachery and cruel deceit abound in Breathe, which is based on a French coming-of-age novel by Anne-Sophie Brasme. The picture really begins to sizzle when Charlie finally recognizes that Sarah isn't everything she seems, a discovery that enrages the young vixen-in-training, who has everything to gain by keeping her real story a secret. But even if Charlie is the obvious aggrieved party, Sarah also feels betrayed: Her yearning for acceptance is so great that she'll stop at nothing to get it. Laurent has sympathy for them both. Even though we can spot the cracks in Sarah's façade right away, we're seduced by her too; Charlie, on the other hand, lacks energy and fire. No wonder she turns to Sarah for everything she lacks, and no wonder Sarah clings to her for stability.

Laurent navigates the story's sharp turn into darkness with unfussy insouciance, and her actresses are right in step with her. As Charlie, Japy is so placid that at first you're not sure she has enough juice to get through the movie. But as her frustration becomes rage, she reveals deliciously dark shadows. In one sequence, she takes a brush to her wet hair — ouch! — with such vehemence that it's a wonder there's any left rooted in her scalp. And de Laâge plays Sarah as a complicated and surprisingly sympathetic villainess. After the falling-out, Sarah lights a figurative match to Charlie's passive blankness: “You drive people crazy and then you act like a beaten dog.” It's a terrifically cruel remark, but she's got a point. Women can be terrible to one another, but they can also hold up the most truthful mirror — the very one whose gaze we seek to avoid.

BREATHE | Directed by Mélanie Laurent | Film Movement | Playhouse, Royal

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