After tracking down a crazed sniper last year, homicide detective Mike Houston opted to leave Boston for the isolated mountains of Maine. He adjusted nicely to chopping his own firewood, relaxing in his log cabin, and simply enjoying the solitude of the mountains.

But then his former partner, Lt. Anne Bouchard, pays him a visit and dangles the words "serial killer" in front of him. And suddenly he finds himself back in the game beside her - though not "officially".

Desperate for money to get her next fix, Cheryl Guerette, a known prostitute and heroin junkie, was last seen climbing into the car of an unknown John. Bouchard suspects that nameless John is a serial killer she's been hunting - a man known to the BPD as the Fisherman. The suspect has been snatching homeless women and prostitutes off the streets from Portland to Boston, and Bouchard needs Houston if she's going to catch him.

Against Houston's better judgment, Bouchard also turns to mob boss Jimmy O'Leary for advice. Not only does O'Leary have a hand in most of the crime that occurs in Boston, but he also knows a few Russian bosses and pimps who are angry that their employees are no longer on the job. With help from the darker side of Boston, Bouchard and Houston hope to locate the Fisherman before it's too late for Cheryl and his other victims.