Anarchy reigns when an unknown toxin turns the peaceful citizens of Ogden Marsh into bloodthirsty lunatics. In an effort to contain the spread of the infection, authorities blockade the town and use deadly force to keep anyone from getting in or out. Now trapped among killers, Sheriff Dutten (Timothy Olyphant) and his wife (Radha Mitchell) and two companions must band together to find a way out before madness and death overtake them.