As a child, Bruce Wayne falls into a well, where he is attacked by a swarm of bats; he subsequently develops a fear of bats. While watching an opera with his parents, Bruce is frightened by performers masquerading as bats, and asks to leave. Outside, the family is targeted by a mugger, Joe Chill, who murders Bruce's parents, leaving him to be raised by the family butler, Alfred Pennyworth.
Fourteen years later, Chill is freed in exchange for testifying against Gotham City mafia boss Carmine Falcone. Bruce intends to murder Chill in revenge, but one of Falcone's assassins does so first. Bruce's childhood friend, assistant district attorney Rachel Dawes, berates him for attempting to undermine the legal system, telling Bruce that his father would be ashamed. Bruce confronts Falcone in a nightclub, where Falcone demonstrates that real power comes from being feared. Bruce decides to travel the world, learning new skills and abilities to confront injustice. In Bhutan, he meets Henri Ducard who offers to train him as a member of theLeague of Shadows, led by Ra's al Ghul. After completing his training and purging his fears, Bruce learns the League intends to destroy Gotham, believing it to be corrupt and beyond saving, having done so with other cities for centuries. Bruce rejects their crusade, and causes a fire that burns down the League's temple. Ra's is killed by falling debris, while Bruce saves an unconscious Ducard.
Posing as a billionaire playboy, Bruce returns to Gotham intent on fighting crime. He develops a base in the bat-infested caves beneath Wayne manor, and takes an interest in his family's company, Wayne Enterprises, run by the unscrupulous William Earle. The company's top scientist, Lucius Fox, introduces Bruce to various prototype technologies including the Tumbler (a heavily armored car) and a protective bodysuit, which Bruce uses to take up the vigilante identity of "Batman". As Batman, he intercepts a drug shipment and provides Rachel with evidence against Falcone, empowering the honest Sgt. James Gordon to arrest the previously untouchable criminal.
Falcone is declared mentally unfit for trial by the corrupt Dr. Jonathan Crane, and transferred to Arkham Asylum. When Falcone threatens to reveal that he has been importing a fear-inducing hallucinogenic drug for Crane's employers, Crane exposes him to the drug while wearing a burlap mask, driving Falcone insane with fear of the "Scarecrow". While investigating Crane, Batman is exposed to the drug and left incapacitated. He is saved by Alfred and given an antidote developed by Fox. At Arkham, Rachel accuses Crane of corruption, and Crane reveals he has been pouring the drug into Gotham's water supply. He doses Rachel with it, but she is rescued by Batman, who leads a destructive chase through Gotham in the Tumbler to escape the police. Batman cures Rachel and leaves her with two vials of the antidote; one for Gordon, and one for mass production. After Crane is arrested, Gordon learns that the tainted water supply is only harmful if inhaled.
During his 30th birthday celebration at the manor, Bruce is confronted by Ducard, who reveals himself to be the real Ra's al Ghul; Bruce expels his guests so they will be safe. Ra's reveals that he employed Crane, and stole a powerful microwave emitter from Wayne Enterprises, that will be used to vaporize the tainted water supply, making the drug airborne and causing mass hysteria and violence that will destroy Gotham. Ra's' men set fire to the mansion, and Bruce is saved by Alfred, who secures them in the Batcave before the fire engulfs the building. As the League's plot commences, Batman rescues Rachel from a drugged-mob and indirectly reveals his identity to her before pursuing Ra's onto a monorail train carrying the emitter toward Gotham's central water source. Gordon uses the Tumbler's cannons to destroy a section of the track and derail the train. Batman overpowers Ra's but refuses to kill him, while also refusing to save him, before gliding from the train car, leaving Ra's to die as the train crashes and explodes.
Batman becomes a public hero, but loses Rachel, who cannot be with Bruce while he is Batman. Bruce buys a controlling stake in the now publicly traded Wayne Enterprises, fires Earle, and replaces him with Fox. Gordon — now promoted to Lieutenant of the Gotham Police Force — shows Batman the Bat-Signal and mentions a criminal who leavesJoker playing cards at crime scenes. Batman promises to investigate and disappears into the night.