While burrowing for oil underground, Snake Probes caused a mysterious green liquid from the Kraken's underground world to leak into the Great River. Meanwhile, Sonic the Hedgehog was fishing from a bridge leading over the Great River when he caught a fish. However, he failed to reel in the fish, which proved stronger than him for some reason, and ended up getting pulled into the Great River. Afterward, Sonic returned from the Great River with the green liquid on him. Upon seeing this liquid's ability to make plants grow rapidly, the Knothole Freedom Fighters set out on the Great River in one of Rotor's boats to find the source of the green liquid. During the trip, however, the group got caught in a whirlpool that pulled them into the underground world of the Kraken.