On Halloween, Scarecrow forces the civilian evacuation of Gotham City after threatening to unleash his potent new fear toxin. Batman tracks Scarecrow to a hideout where he rescues the imprisoned Poison Ivy, who had refused to join Batman's other rogues in Scarecrow's plot. Batman meets with Oracle, who identifies Ace Chemicals as the source of Scarecrow's toxin. Batman investigates the facility but encounters the Arkham Knight and his heavily armed militia. Batman overcomes the forces and locates Scarecrow, who has transformed the entire building into a toxin bomb. Scarecrow reveals that he has kidnapped Oracle, and exposes Batman to the toxin before escaping. Batman inhibits the bomb's blast radius before he is confronted by the Joker.
