Ramona Quimby is growing up. She and Beezus manage to convince their parents to let them stay home alone together after school for one week to see how it goes. When the sisters find their cat, Picky-Picky, dead in the basement and handle the funeral and burial themselves, their parents decide they are responsible enough to take care of themselves. Ramona is especially happy not to have to go to the Kemp's after school any more because Howie's rich Uncle Hobart has arrived from Saudi Arabia. He's the kind of man who thinks it funny to tease kids, and the girls don't like him. There are more changes coming for the Quimbys. Mr. Quimby is almost finished with college, and everyone hopes he'll get a teaching job in the area. It's especially important because Mrs. Quimby is expecting another baby, and she plans on staying home to take care of it. Beezus thinks it will be wonderful to have a baby around to take care of, but Ramona realizes she won't be the littlest any more. She's not sure how she feels about being the middle child. Before she gets a chance to find out, something else changes. Aunt Bea and Howie's Uncle Hobart get engaged, and Beezus and Ramona are to be maids of honor. They only have two weeks to plan the wedding, though, and by the time the wedding day arrives everyone in the neighborhood has become involved. By the time baby Roberta arrives, Ramona realizes, along with everyone else, that "She was winning at growing up."