Taking place on planet Earth, the evil Dr. Robotnik has returned. He's eager to begin his plans for world domination by creating a twisted Utopian vision of Robotnikland. He has a scheme to use the seven Chaos Emeralds to empower the Chaos monster, which grows each time it consumes one of these magical Emeralds. Sonic becomes entangled in this sinister plot as our Hero must enlist the help of his friends to foil Robotnik's every move.
The world within Sonic Adventure DX is typically a Sonic world, featuring bright, diverse landscapes designed for speed and exploration, springboards that propel you to hidden stages, not to mention the thousands of rings to collect and cute animals to save from the clutches of the evil Dr Robotnik.

Sonic Adventure DX features six playable characters to choose from, each with their own skills and abilities. There are 50 massive levels, with bonus round bosses and mini-games. To unlock the mini-games you must either collect all the emblems by completing each main game stage with each character or by completing all 60 missions in the new Mission Mode.