The Riddler is out to control all of prize fighting in Gotham City. He begins by kidnapping and brainwashing top prizefighters with the aid of the Siren. Then, under the guise of Mushi Nebuchadnezzar, supposed boxing champion of Southwest Asia, he challenges Batman to a fight in the ring. But when it becomes clear that the Riddler has no plans to play fair, it's up to Batgirl to help her crime fighting companions.