Assassins Anonymous

"Mark was the most dangerous killer-for-hire in the world. But after learning the hard way that his life's work made him more monster than man, he left all of that behind, and joined a twelve-step group for reformed killers. When Mark is viciously attacked by an unknown assailant, he is forced on the run. From New York to Singapore to London, he chases after clues while dodging attacks and trying to solve the puzzle of who's after him. All without killing anyone. Or getting killed himself. For an assassin, Mark learns, nonviolence is a real hassle"--