Undone by Karin Slaughter

 I've been reading the Will Trent books all out of order as I can find them at the library. This is the book where he meets Sara, a physician and former coroner, to whom he's immediately drawn. Will and Faith are trying to find the psychopath who has kidnapped and tortured several women in Atlanta. They feel like they're spinning their wheels but eventually start piecing together the clues. At the same time, Faith is dealing with health issues and Will is dealing with Angie issues.