It's probably not a good idea to wander the back alleys of any city late at night. Gotham is no exception to this rule of thumb, so when the movie opens with the mugging of a family of tourists who have wandered into the wrong area, we are really not particularly surprised. Neither is Batman; he confronts the muggers and tells them that whatever they have got away with before, times have changed. There's a new superhero in town and he is not going to put up with this criminal behavior. This is just as well because despite an outward appearance of being tough on crime, local law enforcement lacks follow through when it comes to apprehending criminals and local crime bosses know that their bluster is just that - bluster.
Crime Boss Carl Grissom does not know that he has an underling threatening his position; Jack Napier is after his spot at the top. When he does find out he sets a trap for Napier, hoping that he will get shot by corrupt cop Lieutenant Eckhardt. This does not go to plan. The trap is set at the chemical plant, and Eckhardt is killed by Napier in a shoot out. Napier is astounded when the few remaining good cops on the Gotham City Police Force, including Commissioner Gordon, show up at the plant to arrest him. Even more surprising is the arrival of the Caped Crusader, who has come to the plant to put an end to Napier's one man crime wave. They scuffle atop a catwalk and Napier falls into a giant vat of acid below.
Elsewhere in Gotham, Vicki Vale, a photo-journalist, has heard about the new superhero in town and wants to find out the identity of the man behind the mask. She ponders this and hopes that she might learn more about him at the evening's charity gala at the home of eccentric millionaire, Bruce Wayne. She begins to fall in love with him.
Meanwhile, Napier is growing progressively more and more insane. Of course, falling into a vat of acid has not helped. Because of the acid bath he now looks completely different; his hair is bleached green, his skin is pale, and he is more murderous and without morals than ever. The first thing he does on his return to Gotham is kill Grissom and take over the crime syndicate. He also has a new nickname - The Joker. Beyond killing his former boss, though, his plans are less concrete. He tampers with Gotham City Cosmetics and causes many deaths. When Batman realizes that the people of Gotham are literally terrified of washing their faces, he vows to put an end to the madness and neutralize the Joker once and for all. When Joker attempts to kidnap Vicki, Batman rescues her. In the process he realizes that the new criminal in town is actually the old one with a new face, and concludes that the Joker is Napier with an altered appearance. He researches Napier - after all, knowledge is power - and he discovers that Napier was a chemistry whizz in his youth. Batman leaks to the press that Napier/Joker is behind the contamination at the cosmetics factory.
The Joker is not neutralized and comes up with a new and highly unusual plan. He lures the good citizens of Gotham into the streets by leaving huge piles of money there. Once people come out to try to get a hold of some cash for themselves, he plans on gassing them. He is thwarted by Batman once again when the Caped Crusader swoops in and carries the gas-filled balloons away. However, the Joker shoots down his Batwing aircraft with a gun, causing it to crash land and burst into flames. Vicki is taken hostage and taken to the top of Gotham Cathedral, so that Joker's men can pick them up in a helicopter and they can make their get-away. Batman, who has survived the fiery crash, pursues them. There's a struggle and the Joker falls to his death on the street below. Although he generally does not like to be the cause of any death, Batman is not remorseful about killing the Joker, because he has discovered that the criminal was responsible for the death of his parents, and besides, Gotham is a safer place without him, at least for now.
