Black at Heart (Black CATs #3)
Leslie A. Kelly

Even as he devotes himself to catching the Internet's most despicable criminals, Wyatt Blackstone has become a master of detaching himself from his work. But now, after the loss of a vulnerable young agent for whom he cared deeply, Wyatt's renowned icy control is starting to crack. For not only has someone started picking off evil-doers, one brutal murder after another, but the clues to the crimes point to an absolutely impossible suspect: the very woman he thought he'd lost.