Let It Burn
(#10 in Alex McKnight series) "Alex McKnight swore to serve and protect Detroit as a police officer, but a trip to Motown these days is a trip to a past he'd just as soon forget. The city will forever remind him of his partner's death and of the bullet still lodged in his own chest.
Then he gets a call from his old sergeant. A young man Alex helped put away - in the one big case that marked the high point of his career - will be getting out of prison. When the sergeant invites Ales downstate to have a drink for old times' sake, it's an offer he would normally refuse. However, there's a certain female FBI agent he can't stop thinking about, so he gets in his truck and he goes back to Detroit.
While there, he's reminded of something about that young man's case, a seemingly small piece of the puzzle that he never got to share. It's not something anyone wants to hear, but Alex can't let go of the feeling that they arrested the wrong man.
And that the real killer not only got away, but went on to kill again."