Antonio Diego, a mercenary and a member of the League of Shadows, is used as a guinea pig for the steroid like drug Venom by Dr. Jason Woodrue. However, the experiment is in fact a part of a pre-meditated plan by Diego to escape. Although he initially plans to murder all witnesses, he decides to spare scientist Pamela Isley and takes her with him after murdering Woodrue.
Batman hears of the story as well as rumours that Diego intends to take Gotham. However, Gotham already has it's own problems; Victor Fries, a scientist presumed dead after a lab accident, reappears in the form of the villain Mr. Freeze. Meanwhile, Dick Grayson is introduced to local libarian Barbara Gordon, who is also police comissioner Gordon's daughter.
Diego soon appears in Gotham as Bane, empowered by Venom, with Isley secretly working under the identity Poison Ivy. During a shootout with the Gotham police, Isley is killed, enticing Bane to plan revenge by terrorizing Gotham. Meanwhile, Batman captures Freeze.
Bane sees Freeze as a potential ally and breaks him out of prison. Barbara figures of Bruce and Dick's secret identities and then takes up the mantle of Batgirl. Bane uses a stolen atomic bomb as part of his plan. Freeze, realising that it will kill hundreds, betrays him, but Bane mortally injures him.
Batman, Robin and Batgirl confronted Bane atop the Gotham conservatory. During the battle, he is badly injured during a fall but detonate the explosives planted across the observatory, killing himself with the trio escape.
Eric Bana - Bruce Wayne/The Batman
Logan Lerman - Dick Grayson/Robin
Emma Stone - Barbara Gordon/Batgirl
Geoffrey Rush - Alfred Pennyworth
Bryan Cranston - Comissioner James Gordon
Billy Dee Williams - Lucius Fox
Patrick Stewart - Victor Fries/Mr. Freeze
Amanda Seyfried - Pamela Isley/Poison Ivy
Nathan Jones - Antonio Diego/Bane
The series ended with The Batman Forever.