Arkhamverse

Batman: Arkham Asylum
After the Joker assaults Gotham City Hall, he is caught by Batman and taken to Arkham Asylum, which temporarily houses many members of the Joker's gang, who were transferred after a fire at Blackgate Prison. Believing the Joker allowed himself to be captured, Batman accompanies him into the asylum. The Joker's plan is revealed as Harley Quinn takes control of the security and the Joker escapes into the facility, aided by a corrupt guard who kidnaps Commissioner Gordon. The Joker threatens to detonate bombs hidden around Gotham City if anyone tries to enter Arkham, forcing Batman to work alone. Tracking Quinn to the medical facility to rescue Gordon, Batman is exposed to the Scarecrow's fear toxin and hallucinates, seeing Gordon's death and the corpses of his parents talking to him. After fighting off Scarecrow, Batman finds and subdues Quinn before rescuing Gordon. The Joker then directs Batman to the captured Bane, who has been experimented on by asylum doctor Penelope Young. The Joker frees Bane and Batman is forced to fight him, during which Quinn escapes. Afterward, he goes to a secret Batcave installation he had hidden on the island, where Batman restocks his gadgets.

There, Batman learns that the Joker returned to the asylum to gain access to Young, who has been developing Titan-a more powerful version of the Venom drug that gives Bane his strength-intending to use it to help patients survive more strenuous therapies. Young learned that the Joker had been funding her research to create an army of superhuman henchmen; her refusal to hand over the formula precipitated Joker's return to the Asylum. While searching for Young, Batman is again attacked by Scarecrow with the fear toxin, and hallucinates the night of his parents' deaths. After he recovers, Batman destroys Young's Titan formula and rescues Young from Victor Zsasz. An explosion kills Young and the Joker obtains the completed batches of Titan.