Declan Thomas' body temperature is dropping. He never gets sick, never feels pain. An ex-inmate of an insane asylum that was destroyed in a fire, he has the strange ability to step inside a person's madness - and sometimes cure it. He hopes to one day cure his own, but time is running out, as a demonic predator pursues him through a nightmare version of Boston - and when Declan's temperature reaches zero...it's over!

When a mysterious madman returns to claim Boston's sanity, Declan Thomas can only fight him by fulfilling a dark prophecy. With each step, with each use of his abilities, with every ounce of effort he gives to hold onto his sanity, he grows colder. Step by step, moment by moment, closer and closer to zero. With his body failing and his sanity crumbling, Declan balances between falling into madness and falling onto a dinner plate, because Nimble Jack is back, he's hungry, and to him sanity is just a matter of degrees.