Whistler's Hollow, by Debbie Dadey, 2002

When Lillie Mae's daddy didn't come back from the Great War in France, and her Mama was killed in a factory accident, and Aunt Helen made no secret of not wanting her, there was only one place to go: Whistler's Hollow, clear on the other side of Kentucky, to live with Daddy's Uncle Dallas and Aunt Esther. They welcome her warmly, but their young friend Paul does not. And what's Paul always toting around in Uncle Dallas's violin case? Short, moving middle grade historical fiction, with its share of dangers and surprises.