In the quiet coastal town of Saint-Michel, a disturbing scene unfolds deep in the woods as an unknown figure digs beside a hidden shape.
Meanwhile in England, single mother Sarah Gleason sends her teenage daughter Katie on a school exchange trip to the south of France. Before Katie leaves, Sarah reminds her to stay in touch. The trip is supervised by teacher Neil Scott and Sarah's boyfriend Jason Bradley is driving the group to Saint-Michel.
Katie is assigned to stay with the well-respected Morvan family, whose daughter Emma greets her with an uneasy politeness. While Sarah spends a quiet weekend at home, Katie quickly becomes absorbed in to the social life of the exchange students. Parties, alcohol, and tensions within the group begin to surface.
Late one night, Sarah misses a call from her daughter. When Katie suddenly stops answering messages, Sarah's concern turns to alarm. The host family, the school, and the supervising teacher all insist that Katie is simply out with friends. But something about their explanations feels wrong.
Unable to shake the feeling that her daughter is in danger, Sarah flies to France. Once in Saint-Michel, she finds a town reluctant to answer questions. The police appear slow to act, the Morvans seem strangely calm, and students at the school are evasive.
As Sarah begins asking questions herself, she discovers Katie spent her last known night with a troubled local boy named Xavier and another unidentified girl. Surveillance footage soon confirms Katie was in town only hours before she vanished.
Then Sarah receives a message from Katie's phone - one that turns her worst fears into a terrifying possibility.
