Strega — Andrew H. Vachss

It was very dirty work but Burke didn't shock easy. The lower depths of New York was his turf and he was as at home there as a shark in water. But when he was hired
by Strega, a beautiful, steamily sensual woman, to recover a photo of a young boy being sexually abused, he discovered there were depths within depths of depravity--as he found out what unimaginable acts human beings were capable of ... including himself....