Gotham City is in the midst of the holiday season when a corrupt millionaire, Max Shreck, conspires to create his own power plant to further his control over the city. During a speech at the tree lighting ceremony, violence erupts as a gang of circus performers-turned-criminals, led by the grotesque and abandoned child-turned-underworld figure known as the Penguin, lay siege to the crowd. In the ensuing chaos, a mysterious vigilante dressed as a bat confronts the gang and restores peace. Meanwhile, Shreck's mousy secretary, Selina Kyle, uncovers her boss's dark schemes and is nearly killed for it, plunging from a high window. However, she survives and undergoes a dramatic transformation that brings forth her fierce alter ego.

As the city recovers, the Penguin emerges from the sewers, seeking acceptance and the truth about his origins. He manipulates the people's sympathy, striving to establish a place in the upper echelons of Gotham's society. Shreck sees an opportunity in the Penguin's quest and proposes to help him, with the hidden agenda of using him as a puppet to advance his own power grab. They hatch a plan to discredit the city’s beloved vigilante, while the newly empowered woman, now adopting the guise of a feline-themed antiheroine, pursues her own vendetta against Shreck and crosses paths with Gotham's dark defender. Their intertwined motivations set the stage for a confrontation that threatens to plunge Gotham into deeper shadows as they each search for their own form of justice.