Fractured (Will Trent, #2) by Karin Slaughter

When Atlanta housewife Abigail Campano comes home unexpectedly one afternoon, she walks into a nightmare. A broken window, a bloody footprint on the stairs and, most devastating of all, the horrifying sight of her teenage daughter lying dead on the landing, a man standing over her with a bloody knife. The struggle which follows changes Abigail's life forever.

When the local police make a misjudgement which not only threatens the investigation but places a young girl's life in danger, the case is handed over to Special Agent Will Trent of the Criminal Apprehension Team - paired with detective Faith Mitchell, a woman who resents him from their first meeting.

But in the relentless heat of a Georgia summer, Will and Faith realise that they must work together to find the brutal killer who has targeted one of Atlanta's wealthiest, most privileged communities - before it's too late...