 Spin-off of STH3. The Death Egg, the fortress that could Roboticize the entire world with one button, has crashed on Angel Island. Robotnik needs only the Chaos Emeralds to power it up again and return to his road to world destruction. Sonic and Tails need to find the Chaos Emeralds before he does. However, Knuckles thinks that Sonic and Tails are after the Master Emerald, so he is equally determined to stop the duo. But while all 3 are going round with each other, who s gonna stop Robotnik?