I Hear They Burn for Murder - Murder in the Dark, #1

"We're playing Murder in the Dark, Agent." Special Agent Ezekiel Herod knows the game well, but he's never played it quite like this before. Rainer Bryssengur is only a professor of English and Ezekiel doesn't expect to gain any insight from him into his case, only to cross him off the list as a person of interest. Then he meets him and gets a glimpse behind the carefully crafted mask Rainer wears every day to the monster he is at heart. "Which one of us is the liar?" Sometimes even a psychopathic serial killer gets tired of killing people and that's where Rainer is when Ezekiel walks into his office and stirs things up.
The serial killer the media has dubbed The Lamplighter has been dormant because Rainer's heart just isn't in it anymore. But Ezekiel presents him with a new opportunity, a challenge. a game. Rainer sees in him the perfect adversary. They're more alike than either of them suspect and soon Ezekiel gets pulled in deeper than he thought possible, past the point of no return. "Which one of us isn't? That's the real question."