Bruce Wayne saw his parents die when he was eight. When he became older, he trained under Kirigi. Later, he returned to Gotham City as Batman. In his second year of crime fighting, Black Mask sent eight assassins to kill Batman at Christmas Eve. At Blackgate, he encountered Killer Croc who told him that one of these assassins will be rewarded $50,000,000. Bruce came to The Final Offer (Penguin's Hideout) to defeat Deathstroke and the Electrocutioner. He later learned that Black Mask died at Lacey Towers. At the towers, the victim was not Black Mask, but his wife and the murderer was known only as "The Joker". He went to the GCPD to learn more from the National Criminal Database. He came to Gotham Merchants Bank where it was revealed that Black Mask was captured and the Joker is the leader of the 8 assassins. 3 months later, Batman returned to Blackgate and met Catwoman. Years later, he sent the villains to Arkham Asylum. The Joker took over the Asylum and used Titan for himself. Batman defeated the Joker at the prison. About 1 year later, Hugo Strange took a half of Gotham City and converted it to Arkham City. Batman freed Catwoman from Two-Face so he can know what Protocol 10 is. Batman traced a signal to the church where Joker and Harley Quinn live in. The Batman found another signal at the Steel Mill where the Joker is sick. Instead, the Joker is faking. The Joker gave a sample of his blood so Batman and the population can die of sickness. Batman intended to make a cure by contacting Mr. Freeze. Mr. Freeze was captured by the Penguin in the Museum. Batman later freed Mr. Freeze and found a trail of blood which leads him to the league of Assassins. Ra's al Ghul gave him a task to live for a long time. Batman resisted and killed Ra's. Batman took Ra's blood for the cure. Bruce came to the GCPD where Freeze is working on the cure. It was revealed Harley Quinn took the cure. Bruce came back to the Steel Mill and got outnumbered by the Joker and his allies. Bruce realizes that Protocol 10 is a scheme to kill all the villains in Arkham City. Bruce encountered Hugo Strange and realizes Ra's is the reason why Arkham City was built. TYGER later retreated. The Joker took Talia al Ghul and the cure to a theater. In the theater, it was now known that Clayface poses as a healthy Joker while the real one is sick. Batman defeated Clayface and drank the cure. The Joker later died. Harley Quinn was depressed by the Joker's death. Batman attempted to free the cops and defeat Harley Quinn until he got stunned and captured in a Joker robot. Robin followed Batman's tail and Batman disabled bombs. Harley Quinn was later arrested and got very upset since she got arrested. After she got arrested, Arkham City shutdown.