When four young Americans sign up to work as counsellors in a remote Spanish camp, their visions of a fun-filled summer quickly dissipate. As one of the four is seemingly infected with a deadly disease, they begin attacking anything and everything in their path. Before the group even realise what's happening, a rage-inducing virus begins to take hold, spreading rapidly one-by-one among them. Before long, each must fight for their lives, if they have any hope of surviving the night.