The book starts of in the past of Mobius, when Sonic was seven years old and Dr. Robotnik was fifteen years old. In this past, Sonic and Robotnik both lived together with Sonic's Uncle Chuck. Robotnik was always stealing things from Uncle Chuck to make robots in the backyard, and one day he stole parts from Chuck's tractor. When Chuck started it up, he could not control the tractor and he eventually ended up stuck with Robotnik between a wall and the tractor, and Sonic needed to save them. Robotnik was then sent to his room, where once more, he stole appliance parts and made robots. Much later, Robotnik decided he would use a robot to attack Chuck, but the attack ended in Sonic saving Chuck once more. Upset, Robotnik ran away.
Eight years later, Sonic is fifteen years old, and Robotnik is twenty-three years old. Sonic and Chuck haven't seen Robotnik since the day he left. Chuck had given Sonic a dog, Muttski, to play with. Chuck has his very own chili dog stand, Chuck's Chili Dogs, and receives a very large order for two-hundred chili dogs, which is only Robotnik's trap to take Chuck and Muttski away to make them into robot slaves. Sonic realizes what has happened and rushes to save them, when he meets Sally Acorn for the first time, who needs to rescue her father, the king of Mobius.
Together, they successfully save Chuck and Muttski from Robotnik, but Sally is unable to save her father. Sally takes Sonic, Chuck, and Muttski to the secret village of Knothole, which Robotnik knows nothing of. Sonic is asked if he wants to join Sally's group of Freedom Fighters, and accepts.