Knuckles reluctantly makes a deal with Robotnik to turn over Sonic and his family in exchange for finding the Chaos Emerald that will save Mobius. Knuckles soon regrets that he ever trusted the evil dictator after Robotnik begins to follow through on his plans to roboticize the Hedgehogs. Once Knuckles saves his friends from doom, a larger challenge is waiting for them. Dingo has swallowed an emerald and is now a giant monster creating havoc all over the planet. The Hedgehogs and Robotnik have to stop the mutant creature before Mobius falls into certain oblivion.