Whistling in the Dark by Lesley Kagen (2007, Paperback)

Very good story told from the eyes of ten year old Sally. That summer of 1959 Sally's mother ends up in the hospital and Sally and her younger sister Troo are pretty much left to their own defenses. Basically abandoned by their step-father and with an older sister too busy with her own life, Sally can only try to keep promise to their father to watch out for Troo. Mean while there is a child killer on the loose and Sally is pretty sure of 2 things: who the killer is and she is next...