Last to Die by Tess Gerritsen

Three children have managed to survive the murders of their families--and the murders of the foster families that took them in. Why are they being targeted? And who is trying to kill them? That is the at the heart of Last to Die, the newest "Rizzoli and Isles" adventure by Tess Gerritsen. The boy Julian, who saved medical examiner Maura Isles' life in a previous book, is now living at the mysterious (and heavily guarded) Evensong boarding school. When Maura goes to visit him, she is soon caught up in trying to figure out who is trying to kill Teddy Clock, Claire Ward and Will Yablonski, fellow students at the school. And where Maura goes, can Boston cop Jane Rizzoli be far behind? All in all, it's quite the page-turner, with some satisfying twists at the end.