After an experimental gene therapy turns them into monsters, three twenty-somethings band together to hunt down the scientist responsible and force him to make them human again.

After settling in Green Hills, Sonic is eager to prove he has what it takes to be a true hero. His test comes when Dr. Robotnik returns, this time with a new partner, Knuckles, in search for an 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.