In The Dark Knight, viewers are introduced to a new villain known as the Joker. He is a very dangers man who wears makeup similar to a clown along with dyed green hair. The Joker robs a bank owned by the mob. Meanwhile Batman is out fighting various criminals including one in which he thwarts a drug deal among mobsters. The next day police detective Gordon meets with Dent to discuss their strategy to eliminate the mob for good by seizing their money. Dent agrees and goes with the plan.
However a Chinese financier helps the mob avoid this and takes their money to protect it in Hong Kong. When the mob is having a meeting, the Joker shows up and offers to help kill Batman. At first they refuse but eventually give in once they all get arrested by the authorities. Once the Joker begins his attempt to eliminate Batman he begins killing impersonators of Batman to send a message. The Joker threatens to kill people everyday until Batman reveals his true identity.
Over time the Joker commits a series of terrorist attacks and sets up a capture to help execute his plan. He gets corrupt detectives to murder the police commissioner, murder a judge and then kills Rachel Dawes the assistant district attorney who is Dent's lover and also the woman Wayne wants to have romantic ties to as well. In the end Batman eventually fights the Joker and ties him up for the SWAT to arrest him.
He has a final confrontation with Dent who became Two Face after suffering an accident when escaping captivity by the Joker's henchmen. In the final confrontation Dent gets killed and Batman accepts liability for his death. A manhunt ensues and Batman goes into hiding.