The Joker kidnaps a judge, towing him away encased in a giant playing card while the police watch. According to Arkham Asylum's records, Joker has been locked him his room all night. Batman confronts Joker outside the asylum, and the villain turns out to be an Arkham orderly. Joker has bigger plans: to encase several of his enemies in playing cards. The Clown Prince of Crime invites hundreds of Gotham City's important people to the theatre for one final performance. During the show, Batman shows up to try to corral the supervillain.
Legend says that swamp giant Solomon Grundy will return to Gotham City on a Halloween with a lunar eclipse. Supposedly, Grundy will return to get revenge on the descendants of Gotham's founding fathers. On Halloween night, the eclipse begins, and Batman receives word that Grundy is wreaking havoc in Gotham. The caped crusader is skeptical about the legend. Still, he must battle this dangerous villain who is bent on terrorizing certain residents of the city.
When her father, along with other high-ranking Gotham officials, begins to embrace environmental causes after the delivery of mysterious plants, Barbara discovers that they've been replaced with plant-based copies created by Poison Ivy and teams up with Batman to stop her and their own evil clones.