Sonic reluctantly takes Tails with him to the Big City to find some cotter pins for the Freedom Fighters catapults. While in the City, Sonic is nearly eaten alive by his old dog Muttski, now a roboti-sized guard dog in the Junk Heaps. Later, while escaping some Swat-Bots, Sonic and Tails overhear Robotnik explaining his plan to defoliate the Great Forest with a chemical spray and reveal Knothole. After a harrowing chase, Sonic and Tails return to Knothole and reveal Robotnik's plan to the other Freedom Fighters. They come up with a daring plan to stop Robotnik's defoliating scheme that involves Sonic's speed and the catapults.
Sonic is back on Planet Mobius, using his supersonic speed and teenage irreverence to thwart the comedically despicable Dr. Robotnik. Sonic’s idolizing little buddy, Tails, tags along on every fast-action, gag-driven adventure.