In a last-ditch attempt to save their faltering marriage, a professional couple Martin & Kate Badenoch (Cillian Murphy & Thandie Newton) retreat to a beautiful, yet remote and unpopulated island of Dinnish, (U.K.). A place where they once shared a romantic holiday – an island that holds fond memories of happier times.
It is Autumn. The rocky, barren moors are blown by freezing winds, and the generator and radio communication in the couple’s cottage are failing. Relationships are already tense, and anxieties are pushed higher when they lose all contact with the mainland, and find themselves inexplicably stranded and cut off.
After a huge storm, a stranger is washed up on the shore. He has frightening news of cataclysmic events happening in the world outside. But who is this volatile, charismatic American dressed in uniform and carrying a gun. Is he telling the truth? Slowly, the couple become unwitting players in a ménage-a-trois.
In a series of tense twists the captive couple uses all their ingenuity to outwit the stranger and unravel the ‘truth’. But is the truth what they really want to hear? Loyalties divide and merge, paranoia runs high and conflicts bubble to the surface resulting in a violent and shocking conclusion.