Marty had just finished burying a dead robin near the tall wooden fence that surrounded the Hutchinson back yard and the house next door. Suddenly she heard it-knock, knock, knock-three knocks coming from the other side of the wall. For a moment Marty was too petrified to move. Knocking on a wall was something a crazy person might do and some people said old Mrs. Hutchinson was crazy, living alone with an unmarried daughter and seeing...