The big news in Kristy's neighborhood is that the Papadakis family is getting a foster child. The Baby-sitters think taking in a troubled child is a really special thing to do. Kristy's sure the new kid will fit right in. Only Lou (and don't call her Louisa!) turns out to be a terror. She's rough, and tough, and none of the kids want to play with her. Kristy knows that she should feel sorry for Lou. But Kristy's even sorrier that she has to baby-sit for her!