Quincy Sharp, former warden of Arkham Asylum, has taken credit for stopping the Joker's Asylum takeover, and used the notoriety to become mayor of Gotham City. Deeming Arkham and Blackgate Penitentiary no longer suitable to contain the city's criminals, Sharp has both facilities closed and buys out a large section of Gotham's slums, converting them into an immense open-air prison named Arkham City. The facility is placed in the care of genius psychiatrist Hugo Strange — who is secretly manipulating Sharp — and guarded by a squad of heavily-armed mercenaries hired from a rogue private military firm, TYGER Security. The inmates are given free rein as long as they do not attempt to escape. Batman maintains a vigil over the detention city, concerned that the chaotic situation there will get out of hand. Meanwhile, the Joker is stricken with a potentially fatal disease, mutated by his consumption of, and subsequent transformation by, the Titan formula—an unstable steroid serum which has the ability to turn men into maddened monsters.
