An unnamed man quits his job at a chemical company to become a stand-up comedian, only to fail miserably. Desperate to support his pregnant wife, he agrees to guide two criminals through the chemical plant where he previously worked so that they can rob the playing card company next to it. The police inform him that his wife and unborn child have died in a household accident. Grief-stricken, the comedian tries to withdraw from the plan, but the criminals strong-arm him into keeping his commitment.
At the plant, the criminals encounter security personnel, and a shootout ensues in which the comedian's two accomplices are killed. The comedian is then confronted by Batman. He flees by jumping into the chemical plant's waste pound lock and is swept through a pipe leading outside. He discovers to his shock that the chemicals have permanently bleached his skin chalk-white, stained his lips red and dyed his hair green. His disfigurement, compounded by the loss of his family, drives him completely insane and marks the birth of the Joker. He later admits that he is not sure whether this actually happened, as he tends to remember his past differently at different times.
The Joker, after emerging from the canal of chemical waste. Art by Brian Bolland and John Higgins.In present day, Batman goes to Arkham Asylum to talk with the Joker about ending their years-long feud, only to find that the Joker has escaped. The Joker shoots and paralyzes Barbara Gordon and kidnaps her father, Commissioner James "Jim" Gordon. He takes Gordon to a run-down amusement park, where he cages him in the park's freak show. He forces Gordon to view blown-up photos of a wounded Barbara, lying stripped nude on the floor after the shooting, much to Gordon's horror. He then puts Gordon on display before the park's freaks, ridiculing him as "the average man", a weakling doomed to insanity.
Batman's attempts to locate Commissioner Gordon are unsuccessful until the Joker sends him an invitation to the amusement park. Though traumatized by his ordeal, Gordon retains his sanity and moral code, and insists that Batman capture the Joker "by the book" to "show him that our way works". Batman dodges a series of booby traps while the Joker tries to persuade his nemesis that the world is a "black, awful joke" that is not worth fighting for, and it only takes "one bad day" to drive an ordinary man insane.
Batman subdues the Joker and tells him that Gordon is as sane as ever, and the Joker is alone in his madness. He offers to help the Joker rehabilitate in order to end their everlasting war, which Batman fears may one day result in a fight to the death. The Joker apologetically declines, saying it is too late for that. He says that the situation reminds him of a joke about two inmates in an asylum who try to escape. Batman chuckles at the joke's punchline, and as the two old foes share a laugh, he grabs the Joker as police arrive.
