After his base got destroyed, Dr. Eggman spreads terror through the city with the mobile fortress Egg Fort that was hidden underground. Sonic rushes in to help, but he can't reach the high-flying Egg Fort. Chris and the others, exasperated at the fact that they could have reached it with the X-Tornado, are met with the plane arriving to where they are, brought by Tanaka in a trailer. Sonic boards the X-Tornado and assaults the Egg Fort. The great battle with the Egg Fort starts to unfold. (thetvdb.com)