The film begins with Michelle (Mary Elizabeth Winstead) leaving her fiancé and getting into her car. As she drives, she notices a strong beam of light and suddenly finds herself trapped in a bunker with two men, Emmett (John Goodman) and Ben (John Gallagher Jr.). The trio is sealed inside, and Michelle soon learns that they are supposedly in a post-apocalyptic world where a catastrophic event has rendered the outside environment uninhabitable.