I, Zombie

My name is John Doe. I've been dead for ten years. I have no heartbeat, no breath, no smell, just cold, clammy flesh animated by something I don't understand. So I sell my dead flesh to the highest bidder. If the price is right, I'll kill for you, steal for you, or save your life for you. There's no mystery you can't hire me to solve... apart from this one. The bent copper torn apart in his flat by something not quite human. The hidden rooms underneath the Tower of London. The hollow-eyed boxer, Morse, and strange, strange Mr Smith with his head full of the future. And the secret they found. The secret of who I am. A secret so big and black and terrible that it changed everything we thought we knew about existence. And now I'm the only person who can stop the end of all life on this planet...