Previously, in Arkham Asylum, the Joker hatched a plot to take control of the Asylum and trap Batman inside along with many of his enemies among the insane criminals already residing there. Batman has to fight his enemies to gain his freedom allowing him to stop the Joker dropping bombs around Gotham city.The events of Arkham City follows a year on from there.
The director of the Asylum, Quincy Sharp, after becoming, by underhand means, the Mayor of Gotham City, decides that the Asylum and the Blackgate Penitentiary are no longer up to the job of keeping the city's villainous enemies safely incarcerated. This results in their closure, and the slum areas of the city are converted into a large prison to be called Arkham City. The shrink, Hugo strange is placed in charge of the facility aided by a private militia called TYGER security. The rules of the new prison are pretty simple. Inmates can do as they please in return for not attempting to escape. A concerned Batman watches over the ensuing chaos and the Joker contracts a sometimes fatal disease after tippling on a Titan formula which has the effect of turning men into crazed monsters.
Bruce Wayne, Batman's alter ego, declares his concerns about Arkhan City and for his pains is arrested by members of TYGER. He is incarcerated in Arkham with the rest of Gotham's undesirables but Hugo Strange lets drop who Bruce's other identity. Batman's butler, Alfred Pennyworth, arranges an air drop of materials which allow Bruce to assume his Batman persona. And so the fun begins.
Batman has many encounters with diverse enemies and must use his multiple special abilities to defeat their evil intentions. The story features as part of the plot Protocol 10, which is a plan to wipe out Arkham Asylum and everyone in it, leaving Gotham City nearly free from its lunatic element. Of course this is at odds with the plans of the criminal element, and the story opens up into many subplots and encounters featuring a host of characters from the Batman comic universe.
Batman's gadgetry has been upgraded for this game and he has also acquired some new devices such as the Cryptographic Sequencer and access to new ammunition such as smoke bombs. The range of attacks and attack combinations has been expanded as have the counter measures to deflect the multi directional assaults aimed at him, not to mention the good old fashioned man to man encounters.
Among the main cast of comic heros are Quincy Sharp, the Riddler, Victor Zsasz, Bane, Poison Ivy, Harley Quinn, Catwoman, Oracle, Nightwing, Hugo Strange, Two Face, the Penguin, Talia al Ghul, Mr.Freeze, Calandar Man, Solomon Grundy, Clayface, R'as al Ghul, Mad Hatter, Deadshot, and of course Robin and Batman's butler Alfred Pennyworth. Along with appearances from Hush, Azrael, Black Mask, Killer Croc and Nora Fries the wife of Mr.Freeze.
The game is a superbly unlikely romp through Gotham City fueled by some equally unlikely characters even when measured by comic book standards of unlikeliness.