Joker creates a toxin that affects only fish, mutating them into Joker fish. Then, he targets innocent men who refuse to copyright his Joker fish. The Joker also captures Harvey Bullock, and Batman must rescue him and foil the Clown Prince of Crime's insane scheme.

Thanks to a freak accident during a high-speed chase, the Batmobile is virtually demolished. After Batman takes the car to his personal mechanic, Earl Cooper, the Penguin makes his move and tampers with the Batmobile, putting it under his control.