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. Oracle identifies Ace Chemicals as the source of Scarecrow's toxin. Batman investigates the facility and discovers a large militia force being dispatched to occupy Gotham, led by the mysterious "Arkham Knight". Batman locates Scarecrow, who has transformed the entire building into a toxin bomb. Scarecrow reveals that he has kidnapped Oracle before escaping. Exposing himself to the toxin, Batman inhibits the bomb's blast radius before he is confronted by the Joker.
