The story starts at Arkham City, where Harley Quinn has just given birth to a baby with green hair and glowing green eyes... The game fast fowards 6 years. The city of Gotham is celebrating a christmas parade in Gotham Square which Bruce Wayne and Tim Drake are both attending. Meanwhile two guards are monatoring the security cameras of Arkham City when there is a massive explosion in the wall and all the prisoners start to escape. The prisoners attack the parade and start taking hostages. Bruce and Tim quickly divert down an alley way and call in the bat wing which drops down their suits. They then proceed to fight the escaped criminals.