A trip to Robotropolis to rescue the roboticized Overlanders baffles Sonic and Bunnie, as many of the Overlanders haven't even been roboticized! Meanwhile, Kodos has gone over the top, affected by radiation, leading Sonic and Bunnie to assist Arachnis in battle against Kodos as they attempt to make their way through the Great Forest. Is Kodos' condition part of a bigger threat? Can Arachnis be trusted? And just what can Robotnik be up to by allowing the Overlanders to exist free of roboticization?