At a press conference held by Bruce Wayne to declare his opposition to Arkham City, TYGER mercenaries arrest and imprison him in the City itself. Hugo Strange discloses his knowledge of Wayne's dual identity as Batman before releasing him into the prison's criminal populace. While Strange prepares to commence "Protocol 10", Wayne obtains his equipment via airdrop from Alfred Pennyworth, allowing him to become Batman. He first saves Catwoman from being executed by Two-Face, who hopes to gain respect by murdering her. After Joker attempts to assassinate Catwoman, Batman tracks him to his hideout in the Sionis Steelmill, believing Joker may know the truth behind Protocol 10. There, Batman learns that the unstable properties of the Titan formula are mutating in Joker's blood, gradually killing him. Joker captures Batman and performs a blood transfusion on him, infecting him with the same fatal disease.
