Set in the countryside of France, the 19th-century horror pic follows John McBride (Boyd Holbrook), a pathologist assigned to determine if the body of a 14-year-old boy found in the woods is the work of a man or a beast. McBride is then welcomed as a guest into the family home of a local wealthy landowner, Seamus Laurent (Alistair Petrie), and his wife Isabelle (Kelly Reilly), who share that their own son, a friend of the victim, has been missing for two weeks. Distraught and determined to keep her daughter safe, Isabelle finds comfort in the arrival of John while he is forced to confront the horrors of his own dark past.