In the Comics: Gotham gangster Sal Maroni throws acid on attorney Harvey Dent during his trial and his disfiguration brings latent schizophrenia and bipolar disorder bubbling to the surface, giving birth to the villain Two-Face
But in the Movie: Maroni (Eric Roberts) and fellow Gotham goons unleash the Joker (Heath Ledger) on Batman (Christian Bale), Dent (Aaron Eckhart), and Commissioner Gordon (Gary Oldman), and let him go to work on his own. Dent endures his defining deformation when an explosion meant to kill him ignites gasoline that he previously spilled on his face while trying to escape.
Does the Change Work?: Yes. Dent's still a victim of mob brutality, and the added involvement of the Joker his subsequent corruption of "Gotham's white knight" proves to be the lynchpin of the film's extremely satisfying narrative. Furthermore, upgrading him from Bruce's good friend to the personification of his goals gives Dent, and their relationship, much more weight. Plus, an early court scene serves as a nice wink and nod to the original circumstances of Harvey's assault.