Sonic, Knuckles and Tails reunite to battle Shadow, a mysterious new enemy with powers unlike anything they’ve faced before. With their abilities outmatched in every way, they seek out an unlikely alliance to stop Shadow and protect the planet.After settling in Green Hills, Sonic is eager to prove that he has what it takes to be a true hero. His test comes when Dr. Robotnik returns with a new partner, Knuckles, in search of a mystical emerald that has the power to destroy civilizations. Sonic teams up with his own sidekick, Tails, and together they embark on a globe-trotting journey to find the emerald before it falls into the wrong hands.