There's Someone Inside Your House by Stephanie Perkins
It's been almost a year since Makani Young came to live with her grandmother in landlocked Nebraska, and she's still adjusting to her new life. And still haunted by her past in Hawaii.
Then, one by one, the students of her small town high school begin to die in a series of gruesome murders, each with increasing and grotesque flair. As the terror grows closer and the hunt intensifies for the killer, Makani will be forced to confront her own dark secrets.