Suspect (Robert Crais)

Orion: The explosive new masterpiece of suspense from the #1 New York Times-bestselling author.
LAPD cop Scott James is not doing so well. Eight months ago, a shocking nighttime assault by unidentified men killed his partner Stephanie, nearly killed him, and left him enraged, ashamed, and ready to explode. He is unfit for duty--until he meets his new partner.
Maggie is not doing so well, either. A German shepherd who survived three tours in Iraq and Afghanistan sniffing explosives before losing her handler to an IED, her PTSD is as bad as Scott's.
They are each other's last chance. Shunned and shunted to the side, they set out to investigate the one case that no one wants them to touch: the identity of the men who murdered Stephanie. What they begin to find is nothing like what Scott has been told, and the journey will take them both through the darkest moments of their own personal hells. Whether they will make it out again, no one can say.