With the defeat of the Egg Emperor, Team Rose is finally reunited with Froggy and Chocola, while Team Chaotix make a startling discovery about the identity of their mysterious client. Meanwhile, Rouge breaks into Eggman's treasure room only to discover it is filled with capsules holding android copies of Shadow.
As Vector interrogates Dr. Eggman, Neo Metal Sonic makes a grand entrance and it is revealed the robot is the real perpetrator of the recent events. Having collected vital data from all the heroes, Neo Metal Sonic undergoes a frightening transformation into a gigantic monster. The four teams must all join forces to stop the Metal Overlord once and for all...