Batman and Nightwing are forced to team with the Joker's sometimes-girlfriend Harley Quinn to stop a global threat brought about by Poison Ivy and Jason Woodrue, the Floronic Man.

In an alternative Victorian Age Gotham City, Batman begins his war on crime while he investigates a new series of murders by Jack the Ripper.

As Batman hunts for the escaped Joker, the Clown Prince of Crime attacks the Gordon family to prove a diabolical point mirroring his own fall into madness.