Batman: Gotham Knights#54(2004)

In Star City, Green Arrow leads a SWAT team in a raid on the motel that Hush was staying in. They find medical equipment that was used for Prometheus' surgery, but neither Prometheus nor Hush are present. Green Arrow reports what he found during the raid to Batman. He suspects that Hush was able to save Prometheus despite the amount of blood loss. Robin informs Batman that he can't find any trace of Riddler or Joker. He reassures Batman that he isn't alone, and they will be ready when Hush reemerges in Gotham, and Robin can't wait. The Penguin can't believe that anyone would marry the Joker, but Jeannie married him long before the Ace Chemical Plant heist that resulted in his transformation. Jeannie died in a boiler explosion that was declared an accident, but the Joker believes it was revenge because he expressed doubts before the heist and wanted to back out. The mobsters briefly let him think he could get away with it, but they called Oliver Hammet. Hammet abducted Jeannie and held her hostage until Jack went through with the job. But the heist failed when Batman appeared and Jack fell into the vat of chemicals and emerges as the Joker, and when the Joker went back to their apartment, he found the entire building ablaze. The Riddler explains that he knows all this because he used to have a studio apartment across from Jack and Jeannie's apartment building. He saw Hammet carry an unconscious Jeannie inside and set the fire that caused the explosion before leaving. The explosion killed Jeannie and knocked the Riddler out. When Nygma regained consciousness, he joined the crowd outside watching the firefighter's work. Nygma noticed Hammet performing crowd control and the Joker, the latter of whom he later saw two days later at Jeannie's burial. Joker says he is going to find Hammet, talk to him, and then kill him.