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.

Lorelei Circe, aka The Siren, launches a two part plan to become the richest and wickedest woman in Gotham City. First she puts Commissioner Gordon under her stunning spell and orders him to stow away in the Batmobile in order to find out the location of the Batcave as well as Batman & Robins secret identities. Secondly she entrances millionaire playboy Bruce Wayne and implores him to sign over all his wealth and belongings to her.