Once a high-profile District Attorney for Gotham City, Harvey Dent was horribly disfigured by an attack made during the indictment hearing of crime boss Salvatore "The Boss" Maroni. After confronting Maroni with evidence linking him to the murder of a small-time bookie -- most notably Maroni's lucky double-headed coin, which he had accidentally left behind at the scene of the crime -- an enraged Maroni threw a vial of sulphuric acid into his face, burning the left side while leaving the right half of his face untouched.
Miraculously, Dent survived this attack but still bore the acid scars on the left side of his face. Driven insane by his traumatic experience, Dent developed a seperate, more violent personality known as Two-Face, which drove him to embark on a life of crime.
Two-Face is obsessed with duality, and almost all of his crimes are based around the number two. A notable quirk of his is his dependance on the use of Maroni's double-headed coin, one side of which he has marred with a knife to reflect his own conflicted personality. The result of a coin toss can be a matter of life or death to his victims, as he uses the coin to determine whether he will perform an act of good or evil in a given situation.
In The Dark Knight, Harvey Dent is pitted in the role of lead District Attorney for Gotham. Labeled as Gotham's "White Knight," Harvey has been working with Rachel Dawes as they attempt to purge Gotham's criminal underworld, attempting to restore order to the once proud city. Harvey also carries a double-sided coin with him as a lucky charm.
During dinner one evening, Harvey is introduced to Rachel's friend, Bruce Wayne. As the discussion turns to the Batman, Harvey makes a passionate speech of how much he wants to help Gotham, and that the Batman most likely isn't going to want to keep doing the fight forever. These words impress Bruce, who agrees to throw Harvey a political fundraiser, promising that his friends will make sure that when the time comes, Harvey's re-election will be in the bag.
Harvey Dent eventually meets with James Gordon. Though Harvey knows there are some corrupt cops in Gordon's special unit, he also suspects that Gordon has been working in secret with the Batman, and wants in on their plan. Gordon eventually decides to let Harvey in on their plan to seize the Mob's money...only to find that the Mob's accountant, a man named Lau, has taken the funds and secretly moved them to an undisclosed location. Harvey and Jim eventually contact Batman, who goes after Lau on Harvey's word that he'll be able to get him to 'talk.'
Once Lau has been returned to Gotham (as to how, Harvey denies any knowledge to the press), Rachel Dawes handles the questioning of the accountant. Lau works out a deal in which he won't surrender the mob's money, but will tell who his clients are. Lau is held in Gordon's unit to eventually testify against the mob members, who total some 500+ people. All of them are brought into the courtroom, much to the surprise of the Mayor. The Mayor chastises Dent's move, but Dent explains the reasoning: The higher-level mobsters will make bail, but the middle-men won't, and they'll be the ones that will help in this situation. The Mayor is still cautious, cautioning Dent that this plan will make him a target now.
A few days later, Harvey attends the fundraiser Bruce promised to throw, at the millionaire's swanky penthouse apartment in Gotham. Dent is a bit off-kilter at the session, and Bruce makes a few jokes at the expense of Harvey's campaign slogan, but Harvey is a bit more reassured when Bruce explains that Harvey really is the man who says what he means.
Also at the function, Harvey manages to get Rachel alone, trying to get her to give an answer, if she will consider marrying him. Rachel claims she is still unsure, but before Harvey can ask more, he is subdued by Bruce (due to the Joker and some thugs that have come for Harvey). Harvey is hidden, and released after the Joker and his men have left.
However, the attempt on Harvey's life was one of three attempts. Two other persons in on the case have been killed: Police Commissioner Loeb (due to a poisoned drink), and Judge Surillo (killed by an explosion in her car). It appears the case may be over, as the deaths of these two high-profile figures has some running scared. Dent surprises Gordon's unit when instead of hiding, he storms in, demanding that Lau testify as soon as possible. However, given the situation, Lau refuses, claiming that they can't protect him.
A few days later, a public funeral is held for Commissioner Loeb. The Joker has threatened to kill the Mayor, and extra security is called out. However, the Joker and some men disguise themselves, and almost succeed, but instead, end up hitting Jim Gordon.
In the aftermath, Harvey encounters one of the shooters in an ambulance, chained to a stretcher. The man is disguised as a Gotham officer, but it is the name tag on the uniform that catches Dent's eye: Rachel Dawes. When Dent gets no additional information from the shooter, he hijacks the ambulance with the man inside, and drives to a hidden location.
Once there, Harvey calls Rachel, explaining that she isn't safe. Rachel then tells Harvey she'll go to Bruce Wayne's penthouse to stay safe. Harvey then attends to the shooter, having tied him to a chair. Harvey uses a loaded gun, and his lucky coin, attempting to frighten the man to telling what he knows about the Joker. Harvey is suddenly stopped by Batman. Batman then explains that in order to stop the bloodshed, Harvey will hold a news conference the next day, and he (Batman) will turn himself in. This decree upsets Harvey, who yells, "You can't give in!" as Batman walks away.
The next day, Harvey holds a press conference. He attempts to reassure the public, but the people in the room appear to be in favor of Batman turning himself in. In a rather shocking turn of events, Harvey claims that he is the Batman, and is taken into custody.
Harvey is taken to Gordon's special unit, where he is prepared to be taken to the County Jail. Rachel eventually meets Harvey, who explains that he is acting as bait to lure the Joker out of hiding, and that when he strikes, Batman will take him down. Rachel pleads with Harvey to reconsider, but Harvey kisses her, and gives her his lucky coin.
As expected, Harvey's transport is interrupted by the Joker, an also as expected, Batman appears to apprehend the Joker. However, their wild card comes into play when Jim Gordon assists in apprehending the Joker...having faked his death to protect his family.
In the aftermath, Harvey is taken away, but does not make it home. Instead, Harvey awakes, tied up in a room filled with oil barrels, and a wired phone. Harvey can hear Rachel on the other end, and is informed that there wouldn't be enough time to save them both, and that 'their friends' would decide who lives. Harvey attempts to free himself, but in the process, ends up spilling an oil drum, and falls to the floor, the left side of his face and body being covered in the substance. As he struggles to right himself, Batman bursts through the door. Thinking that Batman chose him over Rachel(The Joker gave Batman the locations, but mixed up who was where), Dent is shocked, and calls out Rachel's name as he is dragged from the building. Batman is able to drag Dent outside before the building explodes. However, fire from the explosion ignites the chemicals on the left side of Dent's body.
Dent is taken to the hospital, where he eventually wakes up, to find his lucky coin on a beside table. Seeing one side clean, he assumes that Rachel survived. Upon turning the coin over, and seeing the other side scarred, Harvey cries out, and rips off the medical coverings on the left side of his face.
Harvey refuses any further medical treatments, choosing to remain in intense pain. Jim Gordon goes to talk to Harvey, to find out more information about who took Harvey and Rachel. However, Harvey deep down harbors a grudge against Gordon, thinking that because Gordon refused to take care of corrupt officers in his unit, this is the reason for Rachel's death. Gordon claims he's sorry, but Harvey simply responds, "No. No you're not...not yet."
Some time afterward, Harvey awakes to find the Joker at his bedside. Harvey attempts to attack the clown, but is restrained to his bed. Harvey blames the Joker for what happened to him and Rachel, but the Joker claims that he's innocent: he was locked up in Gordon's police unit, so he couldn't have rigged the explosives. The Joker then attempts to play a mind game on Harvey, claiming that chaos is a fair and just way to expound justice. The Joker then tells Harvey this, by placing a gun in his hand, and allowing him to kill him. Harvey, however, relies on his coin to decide. The coin comes up clean, and the Joker's life is spared. Harvey is then let free, and heads off to seek retribution for his pain.
Harvey first tracks down Detective Wuertz. Wuertz claims he doesn't know who picked up Rachel, but assumes it must have been one of Salvatore Maroni's henchmen. Harvey passes judgement on Wuertz with his coin, and when the coin lands on the scarred side, he kills the Detective.
Harvey next sneaks into Salvatore Maroni's car, questioning him as well. Maroni explains to Harvey that Rachel's driver was Detective Anna Ramirez. Harvey then flips his coin twice. The first for Maroni: who turns up clean. The second for Maroni's driver: which turns up scarred. Harvey then kills the vehicle's driver, and the vehicle flips over (presumably killing Maroni as well).
Harvey next goes to Ramirez, who tricks Gordon's wife into taking herself and her kids to a safe location (which happens to be the same location where Rachel was killed). Ramirez pleads that she didn't know what was going to happen, and due to her Mother's hospital bills, she went along with the scheme. However, her pleading falls on deaf ears as Harvey flips his coin. It lands clean-side up, and he spares Ramirez's life, but knocks her out, before heading to the location.
Once there, he holds Jim Gordon's kids and wife at gunpoint, before calling Jim. Jim eventually arrives at the location, where Harvey explains that he is planning to punish Gordon for his failure to stand up to corruption, which presumably led to Rachel's death. Noting how Gordon reacts as he points the gun at the various family members, Harvey, pulls aside Gordon's son, intent on killing him. "Then, you can tell me you're sorry," says Harvey.
Batman shows up, hoping to reason with Harvey. Harvey reasons that this is not about what he wants, but about what is 'fair,' claiming the world is cruel, and fate is always just a game of chance. Batman explains that it wasn't chance that Rachel was killed: all of them chose to go ahead with the plan (Batman, Gordon, even Dent). Batman then claims Dent should point the gun at those responsible.
Dent then decides to do so, starting with Batman. his coin flips to the scarred side, and he shoots Batman, who falls to the ground. Dent then flips the coin for himself, and it comes up clean (causing him to look pained). When it comes to Gordon's turn, Dent is still intent on shooting Gordon's son. Gordon pleads again, claiming that Rachel's death was his fault, and to punish him instead of his son. Dent explains that his son's death will be punishment enough. However, before the coin flip is completed, Batman (who survived the shot), tackles Dent, knocking him over the side of the building. Batman manages to save Gordon's son, but Harvey appears to have died.
In the aftermath, Harvey's plans to convict the mob will fall apart if word gets out about what he did (it is claimed that Dent killed 5 people, 2 of them cops). As Harvey could be seen as a deranged killer, the mob could use this as a way to declare him incompetent. Batman chooses to take the blame for what Harvey did, and Harvey is buried, considered a hero, as a way to give the people of Gotham hope.