Join the world's greatest detective, Nate the Great, as he solves the mystery of the missing Earth Day robot in this long-running chapter book series that's a favorite for beginner readers WILL THIS CASE ROLL AWAY? The Earth Day Fair is days away, but Nate's classroom project--a robot named Mr. Butler--has disappeared. Nate the Great and his dog, Sludge, take on the unusual case, and they are soon searching high...