Topaz radios for help as the ship he is on, the Seahawk, runs into heavy fog. Back at base, the radio goes dead and the news follows that the Seahawk has disappeared. Dr. Eggman is suspected and when news gets out that he has stolen the ancient map, our heroes put the pieces together and race to the rescue at the center of the Earth!
On an Island at the center of the Earth, Sonic and the gang board the X Tornado and pursue Eggman into the unstable Volcano. There they find the mysterious gem “Harahanekon” lighting up an underground jungle, but Eggman is threatening to set off a chain reaction inside the crasher!
The world is filled with the influence of Sonic & co. People who have been set free by Sonic start spreading the Freedom Movement, while at tournaments people start breaking record after record. Meanwhile, a mysterious stranger appears fearful for the destruction of the two worlds unless Sonic and everyone else are sent home.