Cross My Heart — James M. Matheson

Returning home is never easy. For Fiona Donovan, home is the place she ran away from, never to return again. This trip back to see her sister was supposed to prove that the past didn't have to shape her future. When her sister dies at the hands of an evil man it sets Fiona on a path to find the reasons why. She won't let anything stand in her way. Not the police. Not her conscience. Not even the demons from her own past. She has no idea where her desire for vengeance will take her, or if she'll live to see it through.