Batman

Newspaper reporter Alexander Knox and photojournalist Vicki Vale investigate sightings of "Batman", a masked vigilante targeting Gotham City's criminals. Both attend a fundraiser hosted by billionaire Bruce Wayne, who is secretly Batman, having chosen this path after witnessing a mugger murder his parents when he was a child. During the event, Wayne becomes attracted to Vale.
Meanwhile, mob boss Carl Grissom sends his sociopathic second-in-command Jack Napier to break into Axis Chemicals and retrieve incriminating evidence. However, this is secretly a ploy to have Napier murdered for carrying on an affair with Grissom's mistress, Alicia Hunt. Corrupt Gotham City police lieutenant Max Eckhardt arranges the hit on Napier by conducting an unauthorized raid on Axis Chemicals. However, Commissioner James Gordon learns of the raid and takes command, ordering the officers to capture Napier alive. Batman also appears, while Napier shoots and kills Eckhardt as revenge for the double-cross. During a scuffle with Batman, Napier topples off a catwalk and falls into a vat of chemicals. Although presumed dead, Napier survives with various disfigurements including chalk white skin and emerald-green hair and nails. He undergoes surgery to repair the damage, but ends up with a rictus grin. Driven insane by his hideous appearance, Napier, now calling himself "the Joker", kills Grissom, massacres Grissom's associates, and takes over his operations.
The Joker begins terrorizing Gotham by lacing various hygiene products with "Smylex" – a deadly chemical that causes victims to die laughing. Joker soon becomes obsessed with Vicki and lures her to the Flugelheim Museum, which his henchmen vandalize. Batman rescues Vicki, takes her to the Batcave, and provides her with all of his research on Smylex, which will allow Gotham's residents to escape the toxin. Conflicted with his love for her, Wayne visits her apartment intending to reveal his secret identity, only for the Joker to interrupt the meeting. Joker asks Wayne, "Have you ever danced with the devil in the pale moonlight?", which Wayne recognizes as the phrase used by the mugger who murdered his parents. He shoots Wayne, who survives by hiding a serving tray underneath his shirt.
Vicki is taken to the Batcave by Wayne's butler, Alfred Pennyworth, who had been coaxing the relationship between the pair. After Vicki learns his secret, Wayne chooses to battle the Joker for the sake of the city over their relationship. He then departs to destroy the Axis plant used to create Smylex. Meanwhile, Joker lures Gotham's citizens to a parade honoring Gotham's bicentennial with the promise of free money. This turns out to be a trap designed to dose them with Smylex gas held within giant parade balloons. Batman foils his plan by using his Batwing to remove the balloons, but Joker shoots him down. The Batwing crashes in front of a cathedral, which Joker uses to take Vicki hostage. Batman pursues the Joker, and in the ensuing fight, he identifies Napier killed his parents and thus, indirectly created Batman. Joker eventually pulls Batman and Vicki over the cathedral's roof, leaving them hanging while he calls for a helicopter piloted by his goons, who throw down a ladder for him to climb. Batman uses a grappling hook to attach Joker's leg to a crumbling gargoyle that eventually falls off the roof. Unable to bear the statue's immense weight, Joker falls to his death while Batman and Vicki make it to safety.
Sometime later, Gordon announces that the police have arrested all of Joker's men, effectively dismantling the remains of Grissom's organizations, and unveils the Bat-Signal. Batman leaves the police a note, promising to defend Gotham should crime strike again, and asking them to use the Bat-Signal to summon him in times of need. Alfred takes Vicki to Wayne Manor, explaining that Wayne will be a little late. She responds that she is not surprised, as Batman looks at the signal's projection from a rooftop, standing watch over the city.