
Sonic defends planet Mobius from the evil Dr. Ivo Robotnik.

Robotnik's doomsday project begins a week earlier than anyone had anticipated; the Freedom Fighters prepare for what may be their final battle.

Sonic and Sally encounter the Guardian while on a mission to the big city to replace Nicole's malfunctioning microchip.

Princess Sally and Antoine follow up on a lead that suggests her father, King Acorn, may be alive; Sonic attempts to rescue a captured Freedom Fighter.

Sally is taken prisoner by Robotnik and Snively, who construct a robotized Sally clone.