Mystic River by Dennis Lehane. When Jimmy Marcus's daughter is found dead, his childhood friend Sean Devine is assigned the case. Sean's personal life begins to unravel as his investigation takes him back into a world of violence and pain he thought he'd left behind. His quest also leads him on a collision course with Marcus--a man with his own dark past--and David Boyle, a man who hides monstrous secrets beneath a bland facade. The first quarter of the book is a flashback to their friendship when they were 11 and how each one was affected by one particularly horrible incident. I listened to this on tape and while fascinating was very difficult to listen to.