Sonic and his sidekick Tails are called in when the president of South Island reports that he and his daughter are being held by Dr. Robotnik, who claims he's been forced out of his own city, Robotropolis, by a rival called Metal Robotnik. Skeptical but curious, Sonic and Tails head into Robotropolis to shut down a runaway power generator and confront the impostor, only to find the rival is closer to Robotnik than it first appears. What looks like a rescue mission turns into Sonic walking straight into one of Robotnik's own schemes.