Before we attend the real wedding of the century, we see Barbara with her therapist, discussing her mental state with the wheelchair, and her dreams of getting her revenge on the Joker... oh and the guy she was supposedly dating, who fell of the face of the earth. But never mind all that, Joker and Batgirl are getting married!
The wedding can be described as a shotgun wedding, and then some, with many of Joker's armed thugs consisting of the wedding party. The two go back and forth a bit, Joker gives the par for the course "you're bringing Bat-King down" lines, then revisits his wedding plans from an issue or two back, whipping out a chainsaw, so he can take his soon-to-be bride's arms and legs, so she can't go running around on him.
At this point, Babs pretty much says "fuck it" and goes HAM on Joker's thugs, throwing Batarangs around and what not. Surprisingly, back up arrives in the form of James Jr, who comes in with two grenades, telling Joker to stand down. This gives Babs just enough time to get a few hits in on Joker, as she's not going to look a gift horse in the mouth. James tells "Batgirl" that Mrs. Gordon is free and safe, which allows Babs to go all out on Joker... buuuuut, not so fast.
With Babs fully focused on Joker, James manages to chloroform her, telling her that their mother is still indeed a hostage. With Babs out, James offers Joker a trade. His mother for Babs, if not, he'll kill his sister right then and there, ruining Joker's entire spectacle. Joker is intrigued, but notices that the two live grenades James was holding are gone, and asks about them. James points out that those were fake, but he does have a real one, which is what's going to prevent Joker from screwing him over, as he leaves them with it. Joker is impressed with Jr. to say the least.
Babs soon wakes up in a soon to be familiar scene that we'll see probably five more times, to Joker in a suit, holding a bloody, covered, silver platter, ready to serve up a horrifying surprise.