Precious Blood by Jonathan Hayes

The nightmare of 9/11 left New York City medical examiner Edward Jenner shattered and emotionally scarred. He thought he'd turned away from forensics—and life—for good, but the mutilation murder of a college student is pulling him back. The body of a young woman, nailed to the wall of her East Village apartment, has Jenner convinced that there's a serial killer prowling the city—and a second horrific murder only confirms his most terrible fears. The desperate hunt for a psychopath—and Jenner's troubling obsession with a beautiful, frightened woman who could be the maniac's next victim—is pushing the forensic expert to the limits of his physical and mental endurance.

But as the shadows deepen it gets harder to tell who is the hunter and who is the prey. And which one will live . . . and who will die.