Nobody's There — Joan Lowery Nixon

Furious at her father for breaking up their family, Abbie Thompson acted without thinking and got arrested for malicious mischief. Now the judge has assigned her to volunteer in a program that matches teens with the elderly. But Abbie doesn't get just any elderly person. She gets Edna Merkel, a cranky, difficult woman who's a member of the town's crime prevention group. In fact, Mrs. Merkel is too active a member, and after she brags that she's on to something big, she is attacked and ends up hospitalized. Suddenly the private investigator game is real, and only Abbiewith the help of Mrs. Merkel's indecipherable notebook -- can figure out who did it. But will Abbie get to the assailant before the assailant gets to her?