Destroyed by fire years ago, the infamous Philadelphia State Hospital was known as a warehouse for the criminally insane.

But one man never left.

By night Luther walks Philadelphia's backstreets; by day he roams the catacombs beneath the city. Luther is everywhere and nowhere; he's is in your dreams - and your nightmares.

Then Detectives Kevin Byrne and Jessica Balzano are called to a bizarre murder scene: a man has been killed by a railroad spike driven into his head. But this is just the beginning of a trail of evil that will lead Byrne and Balzano back to the hospital, to a missing girl and to a horror they could never have imagined . . .