Sonic, Sonia, and Manic are the children of Queen Aleena Hedgehog, the rightful ruler of Mobius, and are pursued relentlessly by Doctor Robotnik and his bumbling bounty hunters sidekicks, Sleet and Dingo. As infants, the siblings were separated and placed in hiding to fulfill a prophecy made by the Oracle of Delphius that the triplets would grow up to find their estranged mother, overthrow Robotnik, and take their places once more as Mobius' rightful rulers.
Queen Aleena advises the Hedgehogs to travel to a valley of Mobius so that they can bring about peace between two contingents of the resistance that have split. In the meantime, Robotnik is able to build a dam that is dangerous to the peoples land because of the lack of a cohesive effort to end the construction.
Robotnik is using the local hairdresser, Doo-bot, to get information on the citizens that are against him. Sonia becomes a victim of the Doo-bots trance during a shampoo and while under the spell, divulges important information that could lead Robotnik to a secret base. The Hedgehogs learn that the Doo-bot is equipped with a recording device and dash to retrieve the tape from the Doo-bot before the secret location is disclosed.
A self proclaimed scientist has come to Robotropolis with a device that will reverse the effects of Robotnik's roboticizer. Sonia, Manic and Sonia attend a demonstration of this new technology where Sonia decides she can use it to help her rescue a friend. Sonic, on the other hand, is skeptical that this machine is the real thing and decides to investigate.
Robotnik has arranged a museum exhibit of the Royal family goblets. Knowing that Sonic, Sonia and Manic will want to reclaim their family's treasures, Robotnik expects the heirlooms will serve as perfect bait to finally capture the Hedgehogs. Sonic and his siblings are aware that this is most likely a trap and devise a counter plan of their own to avoid getting caught.
The Hedgehogs vacation is interrupted by the news of Robotnik's latest weapon. They are shocked as the submarine melts the icy landscape from under their feet. The Hedgehogs then scurry to locate the lethal submarine before the entire planet is completely submerged underwater.
On a mission in a distant sector of Robotropolis, the Hedgehogs are informed that freedom fighters have disappeared and are going to be roboticized. Sonic races to save his friends, but he is too late. The group of freedom fighters have been robotisized, including Cyrus' father.
