Batman: Curse of the White Knight is the sequel to Batman: White Knight, which saw the Joker lose his grip on Jack Napier thanks to medication and therapy and brought the character to the forefront of Gotham's reform. A bit part of that reform was Harley Quinn, who once again had the man she fell in love with in the first place, but eventually, their story came to an end once the Joker persona took back over Napier at the end of the book. Now Joker is trying to undo all of Napier's good deeds, and in the process of trying to stop him Batman learns there is more to the story.