True Evil book by Greg Iles

When an attractive new female patient walks into the surgery of Dr Chris Shepard, a busy young doctor in Natchez, Mississippi, his idyllic life is ripped inside out. Shepard's visitor is undercover FBI agent Alex Morse. She tells him his beautiful young wife of one year has been seen visiting a local divorce attorney. And this attorney has a group of clients whose wives and husbands have all mysteriously died. Just as Morse suspected, Shepard knew nothing of his wife's visit. Morse's proposition is simple: will Shepard help the FBI trap the murderer? Published By Hodder & Stoughton on 2007