Story: After Robotnik's defeat at the Floating Island, things returned to normal for Sonic and his friends. Robotnik however, had not been idle, and returned with an even grander scheme to conquer the world.
Robotnik has rebuilt his Death Egg fortress, larger than Sonic's entire world! So powerful is its gravity that it can rip planets from their orbits. Already several planets orbited the huge fortress, and Robotnik would not rest until Sonic's world was in his clutches as well!
Already the world is being drawn to the Death Egg. Sonic has to act quickly to stop Robotnik. Tails has managed to create a working teleport pod that can send Sonic to the Death Egg. There was no time to contact Knuckles, so Tails will stay behind and operate the teleport pod and Sonic will travel to the heart of the Death Egg and destroy it.
But as Sonic was teleporting, one of the small planets surrounding the Death Egg changed course and intercepted Sonic! Sonic found himself on a strange world, surrounded by Badnik robots! Already the inhabitants of this world had been captured and changed into his evil minions. Robotnik had prepared a cunning trap, and Sonic had walked right into it.
Everything had gone as Robotnik had planned. He knew that Sonic would try to get to his new Death Egg, and had changed the creatures called Mips into Badniks. Then by controlling the planet's orbit, he had led Sonic right into his trap!
"HA! HA! Now I've got you, you spiky blue freak! You won't stop me this time!"
Sonic must free the captive Mips, make his way to the new Death Egg, and destroy it quickly. If he fails, the world will belong to Robotnik forever!