15 years after a global apocalypse, mankind is on the verge of extinction. Civilisation no longer exists, food is scarce and most eke out a living by stealing and killing. One boy clings onto life in the desolate British countryside, where staying away from others has been key to his survival. But this self-imposed isolation comes to an abrupt end when he crosses paths with another group of survivors and faces an enemy far more savage than any of them could have imagined.