After Shadow steals one of the Chaos Emeralds, Sonic is blamed for the crime and finds himself on the run from the law. As he does so, he runs into Shadow, and realizes why he's suddenly become a wanted criminal, because Sonic and Shadow look very much alike. As the two collide, Shadow reveals his ability to harness the power of the Chaos Emerald to use Chaos Control, which gives him an edge over Sonic. (thetvdb.com)