London architect Martin Kennedy (Cillian Murphy) and his miserable journalist wife Kate (Thandie Newton) often visit a small, remote, uninhabited island off the west coast of Scotland called Blackholme Island for their holiday retreats. The only dwelling on the island, Fairweather Cottage, is seasonally operated by the owner Doug from the mainland and only reachable by ferry. After previously suffering a miscarriage, Kate's relationship with Martin has become tense, and in an effort to rekindle their marriage they decide on a return visit to the island. A few nights into their stay, the generator in the cottage explodes, injuring Martin's arm and leaving them without electricity. They use the CB radio, their only source of communication to the mainland, to call Doug, who ferries out to help them.