Kisscut by Karin Slaughter

When a teenage quarrel in the small town of Heartsdale explodes into a deadly shoot-out, Sara Linton - paediatrician and medical examiner - finds herself entangled in a horrific tragedy. And what seems at first to be a terrible but individual catastrophe proves to have wider implications when the autopsy reveals evidence of long-term abuse and ritualistic self-mutilation. Sara and police chief Jeffrey Tolliver start to investigate, but the children surrounding the victim close ranks. The families turn their backs. Then a young girl is abducted, and it becomes clear that the first death is linked to an even more brutal crime. And unless Sara and Jeffrey can uncover the deadly secrets the children hide, it's going to happen again...