When police officer Christian Kraus attempts to arrest a serial killer who's been cutting a swathe of terror across London, he's unwittingly infected with something beyond his worst nightmares – a murderous creature that lives inside a human host.As both the physical and psychological effects of the creature deepen, Christian finds himself fleeing from murders he didn't commit, his trail followed by a mysterious military force with seemingly unlimited resources at their disposal. His only hope lies in his best friend and a stranger known as the Professor.But the vicious organism within him has a terrifying life cycle he knows nothing about, and it threatens not only his own survival, but the survival of millions.