Edward Nygma creates the game The Riddle of the Minotaur and makes millions for the company Competitron. He is then fired by his superior, Daniel Mockridge, who wants the profits for himself. Nygma vows revenge, and two years later, he takes up the mantle of the Riddler and traps Mockridge inside a life-sized version of the Minotaur maze. Batman's sympathy is with Nygma, but he and Robin have to stop him before he kills Mockridge, despite the fact that Mockridge cannot legally be brought to justice. Regardless, Mockridge, despite the resulting rescue, is left in a permanent all-consuming fear of Nygma's return for revenge.

When a Batman impersonator appears in Gotham City, the real Batman deduces that Karl Rossum is somehow involved and confronts the inventor. The other Batman, a duplicate, then shows up and a battle between the two takes place. After the duplicate Batman escapes, it begins its campaign to recreate H.A.R.D.A.C.'s goals of a robotic society.