If there's a problem in school, there's no substitute for the world-saving substitute teachers of the S.O.S.! This is the first book of this hilarious, highly illustrated early chapter book series. When Milton Worthy learns his classroom's pet ferret is the evil mastermind behind a dastardly plot for world domination, it's more than just about any kid could handle. But then not every kid is the son of a member of the super-secret, super-awesome Society of Substitutes! Now it's up to Milton and his substitute teacher mom to save Beacher Elementary School before time runs out. HarperChapters build confident readers one chapter at a time! With short, fast-paced books, art on every page, and milestone markers at the end of every chapter, they're the perfect next step for fans of I Can Read!.