The movie begins showing the goings on in Gotham City: it' s to real mess. There to are to lot of fake Batmans: they show AP at crime scenes and get killed. But the true Batman is always in action, and he' s not halo: Gotham City has to new District Attorney, Harvey Dent. His girlfriend is Rachel Dawes, who had to relationship with Bruce Wayne (a.k.a. Batman).
Together, Batman and Dent face the crime: when Gambol, the main mob boss, decides to pool all the mob money (billions of dollars) in China and sends Lau (to crooked accountant) to Hong Kong, Batman is able to follow Lau and bring him to Gotham. Dent uses the information taken after his capture to round up to lot of criminals (even Sal Maroni!): to great victory for justice.
But peace does not last: The Joker, to new criminal, reveals himself asking Batman to take his mask off or he' ll start killing people. He says he does it for the mob: he wants their money back, and in exchange wants half of it for himself.
The Joker kills loads people, but decides to go higher and kidnaps both Rachel Dawes and Harvey Dent: Batman has to decides which one to save.
As part of his plan, Joker gets captured; batman rushes to Rachel to save her, but the Joker has lied, and he ends up saving Harvey Dent, who loses his mind completely when he discovers that not only Joker escaped, but has set on to fire the money and the police building.
Joker announces that the Mayor has to die, or he' ll blow up Gotham' s Hospital. Dent decides to hunt down anyone who was involved in Rachel' s kidnap, and kills people too: he finds Maroni and kills him, just after Maroni (worried about Joker' s crazyness) has said to Batman to where to find the Joker. Meanwhile, the clown blows up the hospital.
Now Joker actually runs Gotham City, I know he tells people that they have to deal whit him or to leave. Two ships of pepole leave the metropolis: one full of criminals, and one full of innocents. Joker stops the ships and announces that he' ll blow both the ships up at midnight, unless one ship blows the other up (they both have detonators).
Dent finds Commissioner Gordon, who got corrupted (but is still "good") and inevitably led to Rachel' s kidnap. Dent threatens him with his gun, but Batman arrives and dives him into to hole in the floor, apparently killing him. Then Batman decides to go on the run: he wants to pretend he killed the people Dent killed, because he thinks former-D.A.' Gotham needs it' s s image untarnished.
Meanwhile, Joker has failed, and he goes in prison. The End...