"Finn Caspian, his three best friends, and his robot Foggy are excited to explore a brand-new planet . . . until Finn's mom makes them bring along an annoying new robot named Voltronix Zu. Putting up with Voltronix's bragging is bad enough, but when he accidentally turns the planet inside out, the Explorers get attacked by angry rock giants! Can the four friends find a way to save the planet--and the bubble aliens who live there--before Voltronix causes a volcanic disaster?" -- publisher description.