Hitman Rob Shaw travels to a remote location after a distress call from his ex-wife. Upon arrival, he is met by his estranged father Jim, an ex-director of the Ministry of Defence, his ex-wife, her new husband and Rob’s two young daughters. Jim explains that a global nuclear event is imminent and invites Rob to join them in a bunker beneath the house. Rob rejects the invitation and attempts to leave just as the bombs begin to fall - he has no place or purpose in this new reality. However, when an anarchic gang of ex-soldiers take control of the bunker, his skills and dangerous mindset become the very thing the family needs.