On a dark night in Gotham City, a family of tourists decides to take a shortcut to wherever they're going. They get mugged before we can say, "Look out behind you!" Now, we don't want to blame the victim (which is what everyone says right before blaming the victim) but did they really think that a grungy back alley would be the best route to their destination?
One person doesn't blame the victim…and that person is Batman, a man who dresses up as a giant bat. He intimidates the muggers by getting his masked mug up in their mugs (are you keeping track of all these mugs?) and telling them to pass along a message: there's a new bat in town, and he's tough on crime.
Meanwhile, the mayor, the DA, and the Gotham City Police Department are pretty soft on crime. If they're the long arm of the law, the hand at the end is holding a feather duster and tickling crime. In other words, the organized crime boss of Gotham, Carl Grissom, laughs in the face of law enforcement.
Grissom has someone laughing behind his back, though: his flunky Jack Napier. Napier wants to take over the business, but when Grissom finds out, he plots a trap for Napier, hoping he'll get shot by the corrupt police officer, Lieutenant Eckhardt.
At the Axis Chemical plant, all hell breaks loose for everyone involved. Eckhardt is killed in a shootout with Napier. Napier is taken by surprise when the few good cops on the force, led by Commissioner Gordon, show up to arrest him. And Napier is even more surprised when a man in a giant bat costume tries to stop his crime spree. In a scuffle with Batman, Napier falls off a catwalk into a giant pool of acid.
Elsewhere in Gotham, a photojournalist named Vicki Vale wants to find out who the masked bat-man is. What could his name be? Manbat? Batperson? Der Fledermaus? Vale hopes to ferret out the bat's identity at a charity gala at Wayne Manor. It's there where she meets the eccentric bajillionaire Bruce Wayne.
While Vicki is starting to fall crazy in love with Bruce Wayne, Jack Napier is starting to just go crazy. (Being dropped into boiling acid will do that to a guy.) Napier emerges from the acid with a new pale skin tone, green hair, and a new nickname: Joker. Joker proves to be a real wild card (hey-o), and he wastes no time killing Grissom and taking over the crime syndicate.
From then on out, Joker's plans are less clear. He tampers with Gotham City's cosmetics, causing the deaths of many women and models. The city lives in fear of washing their own faces. Batman must stop this crazy zit-inducing madman. When Joker vandalizes a museum and tries to kidnap Vicki, Batman swoops in and rescues her.
He soon realizes that Joker is the new face of Jack Napier. Doing research into Napier's past, he learns Napier loved chemistry, and he leaks Joker's cosmetics plot to the local news.
Joker cooks up a new scheme: lure the citizens of Gotham into the streets by dumping cold hard cash onto the pavement, then gas them to death. Finally: a diabolical plan that makes sense. Batman ruins this plan by swooping in on his Batwing and carrying off Joker's gas-spewing balloons.
Because the Batwing is the flimsiest aircraft since the Hindenburg, Joker shoots it down with a gun, and Batman crashes and burns. Joker takes Vicki hostage and drags her to the top of Gotham Cathedral, where he waits for his men to rescue him in a helicopter.
Bad idea, Joker. Bats love bell towers, and Batman pursues Joker to the top. After a struggle, Joker falls to his death on the streets below. Batman doesn't like killing people, but considering he found out that Joker, then Jack Napier, was responsible for the death of his parents, Batman isn't too broken up about it.
Later, Batman presents Commissioner Gordon with the Bat Signal. If they need him, they need only to shine it into the sky. Gotham is safe…for now.