Red Rain — Patrick J. O'Brian

A serial killer chooses victims across the state of New York from all walks of life, prompting state police investigator Terry Levine to head up a task force devoted to finding the man responsible for stabbing or shooting seemingly innocent people.

Teaming with a detective from Buffalo, he quickly discovers the man dubbed the Sin Killer by the local media is intelligent and crafty, leaving no traces of evidence at the crime scenes. Levine questions whether the murderer is a transient, a trucker, or worse, an officer of the law. Another element compounds the investigation when Levine discovers four similar murders occurred in the state of Montana several years prior.

Acting more like a vigilante than a man fulfilling his own fantasies, the Sin Killer leaves police a clue with each victim, written in the victim's own blood. As Levine closes in on a suspect, his instincts tell him the man doesn't fit the profile. He decides to conduct his own investigation without assistance from the task force or his own department, leading him down a perilous path in a search for the truth that might cost him his life.