Fractured by Karin Slaughter

Abigail Campano returns to her home one afternoon to find her daughter murdered, with the attacker still standing over her body. Abigail fights him with all the strength she has, killing him in the process. The Atlanta police then arrive, along with Georgia Bureau of Investigation agent Will Trent. Will sees something at the crime scene that the other detectives miss and soon they are looking for a kidnapped teenage girl who probably doesn't have long to live. Complicating the case are the girl's father (who knows Will from when they were both in the Atlanta Children's Home in their youths) and a new partner named Faith Mitchell (who doesn't exactly trust Will since he made a case against crooked cops, including her mother). Fractured is Slaughter's second book featuring Will Trent. The first is Triptych which I haven't read. I liked the character of Will a lot and definitely want to go back and read Triptych when I have time.