Doctor Robotnik has taken control of the enormous Mount Mobius and turned it into a new mechanical base. Using the lava in the volcano below as an energy source, Robotnik's new Veg-O-Fortress serves as the perfect Badnik Processing Plant, churning out new Badniks at an alarming rate. Sonic the Hedgehog and Miles "Tails" Prower arrive by bi-plane for an aerial assault, but are shot down with Sonic plummeting into the sea. Fortunately, he is able to access the base through the sewers and so must take down Robotnik's operation from the inside. Unfortunately, with the power of the Chaos Emeralds required to keep the fortress working, Robotnik has constructed an elaborate pinball system to keep the hedgehog at bay and the Emeralds safe.