New Echidna in Town (Chaos Emerald Crisis, Part 3) Sonic Underground : Season 1 Episode 29

Knuckles reluctantly makes a deal with Robotnik to turn over Sonic and his family in exchange for finding the Chaos Emerald that will save Mobius. Knuckles soon regrets that he ever trusted the evil dictator after Robotnik begins to follow through on his plans to roboticize the Hedgehogs.