Three privileged girls at a cloistered New England boarding school find their social lives thrown into turmoil by the arrival of a manipulative new student, and an affair that spells the end of innocence. With the arrival of fall, Fernanda (Rooney Mara) returns to Tanner Hall to complete her senior year. Fernanda has always been the most level headed of her small trio of friends - which includes mischievous Kate (Brie Larson) and spitfire Lucasta (Amy Ferguson) - though the unexpected appearance of embittered, emotionally-damaged new girl Victoria (Georgia King) finds the subtle cracks in their longtime friendship suddenly beginning to show. Almost immediately after arriving at Tanner Hall, Victoria has managed to turn the three friends against one another. And by all appearances, she's just getting started as Fernanda finds herself increasingly drawn to Gio (Tom Everett Scott), a married family friend. As the upheaval in Fernanda's social life starts to clash with the pangs of first love in her private life, each of the girls begins to realize that the support of good friends will be the factor that helps them make the successful transition into womanhood.