Dexter in the Dark

Crime scene investigator Dexter Morgan is not unaccustomed to seeing evil deeds--particularly because he commits them himself. But at a particularly disturbing scene, he realizes hes being hunted by an adversary more sinister than hes ever faced.

From The Publisher:

In his work as a Miami crime scene investigator, Dexter Morgan is not unaccustomed to seeing evil deeds...particularly because, on occasion, he commits them himself. Guided by his Dark Passenger (the reptilian voice inside him), he lives his outwardly normal life adhering to one simple rule: he only kills very bad people. But Dexter's happy existence is turned upside-down when he is called to a particularly disturbing crime scene at the university campus. Dexter's Dark Passenger immediately senses something it recognizes, something utterly chilling, and the Dark Passenger--mastermind of Dexter's investigative and homicidal prowess--goes into hiding.
Dexter is alone for the first time in his life, and he realizes he's being hunted by an adversary more sinister than anything he's ever faced. Dexter must summon his sharpest investigative powers not only to pursue his enemy, but to locate--and truly understand--his Dark Passenger. It is nothing less than a search for his own dark soul...fueled by a steady supply of cream-filled donuts.
Macabre, ironic, and wonderfully entertaining, DEXTER IN THE DARK goes deeper into the dark psyche of one of the freshest protagonists in recent fiction.