Even though the Earth Day Fair is just a few days away, Nate's robot Mr. Butler from his class project has vanished. Taking on the odd case, Nate the Great and his dog Sludge start looking everywhere within and outside the school. Will Nate track down the robot before the fair? The Nate the Great chapter book series, ideal for Common Core, will inspire kids to solve problems, learn about STEM subjects, and use reasoning to solve riddles.