Keira Knightley and Tobias Menzies Photo

From: Photo Flash: Keira Knightley, Elizabeth Moss Lead THE CHILDREN'S HOUR

When a troubled teenager starts to spin a web of deceit, all around her are soon caught up in it. Karen Wright (Keira Knightley) and Martha Dobie (Elisabeth Moss) have worked for years to establish their all-girls boarding school, and now, with the school flourishing and Karen on the verge of marriage, their lives and loves finally appear secure. However, when malicious student Mary runs away from the school and seeks to avoid being sent back, she draws on hearsay, gossip, and her own imagination, to concoct a story that threatens the school, the marriage, and their entire futures.