Sarah (Anne Parillaud) is struggling to come to terms with the death of her teenage son. One night, driving through the darkness, she almost hits a young man, Arthur, who runs into the road bloodied and terrified. He claims to have been attacked by a mysterious assailant, a burglar who is caught in the act and who is determined to kill him so that he cannot be identified. Moved by the boy's plight, and painfully reminded of her own child, Sarah takes Arthur in and vows to protect him. Only when it is too late to turn back does she realise that all is not as it seems, and the road she has chosen to take may turn out to be more dangerous than she could ever have imagined.