Hattie Owen enjoys the familiarity of her small-town life, but during the summer she turns 12, her world is turned upside down with the arrival of an uncle no one has ever spoken about. Now that Hattie’s uncle’s “school”—an institution for the mentally disabled—is closing, Hattie's family must deal with a childlike young man whose existence they’ve denied for years. And Hattie experiences a summer that expands her world in the most unpredictable ways.