John Cain has been working Homicide long enough to get hard to pretty much anything; even wrenching personal loss. Today, it all gets too much. Today, he gets assigned something that finally breaks through his defenses - a child killing that hits horribly close to home. Until now, he's been a good cop, a cop who goes by procedure because it's the best way to ensure that scum go to prison. Today, he makes the parents of the victim a chilling promise. He will find the killer using any means necessary. And the killer will not get away with it. Whatever happens. How much of a monster do you have to become to hunt monsters?