After settling down in Green Hill, Sonic is eager to prove that he has what it takes to be a true hero. He faces another test when Dr. Eggman and his new sidekick, Knuckles, return to search for an emerald powerful enough to destroy civilization. This time, Sonic teams up with his own sidekick, Tails, to embark on an adventure around the world in hopes of finding the emerald before it falls into the wrong hands.