A riot in the Slab has led to total chaos. The Joker has taken control of the joint, and Black Canary's the lone hero trapped within its impregnable walls. Batman and Nightwing enter the fray, but the Joker's ready for them. It's the end of The Slab as you know it — it's only a question of who will go down with the ship.
Oracle blames herself and Nightwing for the situation at the Slab, where the Joker has started a full-scale riot and 'Jokerised' most of the prison population. Shilo Norman and Dina Bell are trapped inside, and have to fight their way out through the Aqua-Block, which houses such man-eaters as Orca and King Shark. Meanwhile, the Joker sets the next stage of his plan in motion, priming Black Mass to cause a devastating chain reaction which sucks the prison into a black hole. Batman and Nightwing, newly arrived on the scene, are warned of this plan by the Black Canary, and the three are helped to escape by Blue Beetle.