After Sonic has settled in Green Hills, Sonic is ready for more freedom, and Tom and Maddie agree to leave him at home while they go on vacation. But they hardly leave when others. The robot returns, this time with a new partner, Knuckles, in search of an emerald that has the power to build and destroy civilizations. Sonic joins his friend Tails and they go out together to find the emerald before it falls into the wrong hands.
