Carl Grissom was the most powerful crime lord in all of Gotham City. He had a mistress named Alicia Hunt who was secretly having an affair with Carl's "number one guy" Jack Napier. Carl had several members of the Gotham City Police Department on his payroll, including a corrupt lieutenant named Max Eckhardt.
When the recently-elected District Attorney Harvey Dent begins to make connections between Grissom and Axis Chemicals, Grissom panics, knowing that the evidence stored at the factory is enough to have him sent to the electric chair.
Lt. Eckhardt, who never liked Jack Napier, and wanted to see him brought down, told Grissom about the affair that Jack was having with Alicia. Without revealing that he knew the truth, Carl assigned Jack to a special project. He wanted Jack to go to their front company Axis Chemicals and remove all incriminating files before the the police had the opportunity to raid the facility. What Jack didn't know was that Grissom had already cleaned out the plant, and had ordered Lt. Eckhardt to kill him. The set up did not go as neatly as Grissom would have liked. Commissioner Gordon caught wind of the incident and interceded before Eckhardt could take Napier out. Compounding the issue was the appearance of the nocturnal vigilante, the Batman. Batman struggled with Napier, but ultimately Jack fell into a vat of toxic chemicals. Napier survived the accident, but was horribly scarred and hopelessly insane.
After a futile attempt at reconstructive surgery, Jack returned to Carl Grissom's penthouse for revenge. He couldn't believe that Carl would have him rubbed out over a woman. Carl tried pleading with the man, holding up his hands saying, "Jack, listen. Maybe we cut a deal".
As Jack stepped into the light, he removed his fedora and said, "Jack? Jack's dead, my friend. You can call me... Joker. And as you can see -- I'm a lot happier now." At which point, Jack produced a revolver and shot Grissom several times in the chest, killing him.
- Grissom character's inspiration was from Batman's comic book gangster enemies Rupert Thorne and Sal Maroni. Interestingly enough, an earlier draft of the script included Rupert Thorne in Grissom's place, having sent Joe Chill to murder Thomas Wayne, whom had been running against Thorne for City Council.