The blue hedgehog and the red echidna were sworn adversaries in Sonic 3, but in the platform adventure Sonic & Knuckles, Knuckles realizes that he's been just a pawn in the schemes of Dr. Eggman (aka Dr. Robotnik). Knuckles, the former adversary, now supports Sonic to chase the common enemy, and each must use their strengths to acquire the priceless Master Emerald and save Angel Island.