Dr. Eggman is once again on the move, this time with a liquid entity known as Chaos. His plan is to collect the seven Chaos Emeralds and use them to ignite Chaos' most powerful form. He has also created the Egg Carrier, a giant air fortress from which he carries out operations.
Sonic is on vacation in Station Square when he encounters Chaos, and teams up with Tails to collect the emeralds and save the day before it's too late.
Tails is helping Sonic on his adventure, while trying to prove his worth to Sonic and to himself. His missions involve racing Sonic, or piloting the Tornado II.
Knuckles is out to find the shards of the Master Emerald. After it is shattered and Chaos is released, the shards fly in all directions and he cannot rest until it is put together once again.
Amy Rose is on the move when she finds a little Flicky bird, and moments later is being chased by Eggman's seeker robot, Zero.
Big the Cat, a new character, is off looking for his best friend Froggy (Kaeru-kun in Japan) when Froggy hops away one day.
E-102y (Gamma) is a robot in Eggman's brand new E-series. He faithfully fulfills Eggman's orders until he encounters Amy, and afterwards he takes it upon himself to free his E-series siblings.
Chaos is a liquid god who protects the mysterious creatures known as chao. In a rage, he can use the powers of the chaos emeralds to become Perfect Chaos and cause global catastrophe.
Tikal is an echidna girl from the past who befriended Chaos and tried to stop her power-hungry father Pachacamac from going after the emeralds. She failed, and Chaos took on his most powerful form in a harsh fury. She sealed herself and Chaos inside the Master Emerald, where they remained until Eggman shattered it...
Did you know Tikal is a place in Guatemala, South America, wherein lies a pyramid that the echidna pyramid structure's design was based on? :) Pachacamac is named after an archaeogical site in Lima.