After the final stage of human testing goes horribly awry, the test subjects of the fictional pharmaceutical company N-Gen become violently ill. As the side effects worsen, the test subjects become increasingly violent until they are little but marauding beasts. Worse yet, their bites are infectious and in short order London is overrun with hordes of bloodthirsty monsters. Cole, a mercenary for N-Gen and a hardened killer, is searching for Angela Mills, the only hope of a cure for this plague which threatens the globe. As the only test subject who did not suffer side effects, her immunity holds the key to preventing a worldwide apocalypse. Cole's mission is complicated by chaos, continual attacks by the infected, and the virus slowly overtaking his own body.