Maisie Williams and Florence Pugh star in this British drama written and directed by Carol Morley. Lydia and Abbie (Williams and Pugh) are best friends at their all-girls boarding school but they are very different people; Lydia is quiet and introverted while Abbie is ambitious and popular. After Abbie jeopardises her friendship with Lydia by sleeping with her brother, a fainting epidemic breaks out at the school and people are left wondering whether the mysterious Lydia could be the key...