Nobody panics when things go according to plan, even if the plans are horrifying. If I tell the press that tomorrow a gangbanger will get shot, or a truckload of soldiers will get blown up, nobody panics. But when I say one little old mayor will die, everyone loses their minds! Introduce a little anarchy, you upset the established order, and everything becomes chaos. I am an agent of chaos. And you know the thing about chaos, Harvey? It's fair. — The Joker in The Dark Knight

Moral darkness permeates Christopher Nolan's The Dark Knight. The Joker, Batman's antithesis, returns to his unsavory blend of homicidal insanity and nihilistic artistry, first seen in the 1940 Batman comic book, but softened in his subsequent appearances. Gone is the whimsically murderous trickster of precise origin, the clown prince of crime as portrayed in movies, the Batman television series, and many of the DC comic books. Replaced by Heath Ledger's chillingly amoral, incomprehensibly insane, and powerfully corrupting scion of the Devil, no one, including us, is left laughing now.

Throughout The Dark Knight, one question propels the story with its increasing urgency for an answer: how can Batman and Gotham city combat the irreconcilable evil embodied by The Joker without resorting to evil themselves? Batman, Lt. Gordon, and District Attorney Harvey Dent (Aaron Eckhart) must answer it in their own way as The Joker forces them into an ever narrower space for dealing with his escalating chaos and body count. With his smeared makeup, stringy hair, cruelly scarred mouth — and ever-changing story as to how he received his permanent smile — Ledger's Joker is so evil, so anarchic, and so corrupting in his influence, there is no middle ground for goodness and morality to easily stand on. A human Thanatos unfettered by guilt, he makes Hannibal Lecter and the Jigsaw Killer look like Abbott and Costello. The only way to stop him is to murder him; at least, that's what he really wants. But will Batman put aside his moral code to do it? More importantly, do we want him to?

This is not a film for children. It is bleak and unrelenting in its depiction of endless violence that cannot be stopped by the prescribed ways for superheroes, government officials, and the righteous. Like the senseless violence of our times, The Joker is senseless in his motivations, though they make perfect sense to him. He simply has a need to disrupt and corrupt everything and everyone around him, especially Batman. Alfred (Michael Caine) explains it best: "Some men just want to watch the world burn." And Gotham City, as well as Batman's reputation, and his conscience, is burning.