While on vacation, Sonic The Hedgehog, making a discovery on Angel Island, calls his friend Miles “Tails” Prower so they could investigate it together, not realizing that he has gotten himself possessed. The self proclaimed demon, Exezar, using Sonic’s body, goes on a mission alongside his only demon friend, Oxiel, to revive the physical body of himself and his ally, Avares… but, do the both of them have the same goal in mind? Waking up from the commotion caused by Exezar on Angel Island, Knuckles The Echidna rushes to the rescue of the Master Emerald. His badniks have made the same discovery as Sonic, and with Metal Sonic sent away to collect the Chaos Emeralds, Dr. Ivo “Eggman” Robotnik, travels to Angel Island to confirm his badniks’ discovery with his own eyes, only to find himself tangling with the Heroes on the way and, later, Exezar's companion, Oxiel.