Spinning out of the events in Battle for the Cowl, Gotham City is in chaos and the villains of Arkham Asylum are running amok. One such villain is the evil Doctor Phosphorus who seeks out another scientist in this one-shot to help him grow even more powerful. But when that scientist is Kirk Langstrom, a.k.a. Man-Bat, Doctor Phosphorus – and all of Gotham – will get much more than they bargained for!