At the end of a screening of The Dark Knight earlier this week, a couple of the viewers were discussing whether it will be nominated for an Oscar — for best picture.

There's been plenty of talk about an Oscar nomination for the late Heath Ledger for his performance as the Joker. And such talk is perfectly reasonable. He gives a bravura performance in the movie, the kind that makes you think of an actor in an entirely different way, that makes you wonder where in his resume we had any inkling that such a turn was possible.

But best picture is something else. Costumed crime-fighter stories are meant to be escapist fare, cartoon-like — big at the box office but not carrying the sort of prestige that the motion picture academy likes its award-winners to bring along. It's nonsense, of course — Danny DeVito in Batman Returns gave as stirring a performance as any ''serious'' actor at the time — but it happens.

The Dark Knight could change that thinking once and for all. Those guys talking about a best-picture nomination will not be alone.

The Dark Knight is a big, thoughtful, pain-laced, violence-streaked, unsettling movie where Ledger's performance is one of many virtues.

It has one of the best bank-robbery sequences I've seen in a movie, and a car chase that is riveting, even though bank robberies and car chases are movie staples.

It pushes the Joker — and, with him, Batman — beyond the conventions of good guy/bad guy into a debate on the nature of heroism (and villainy), of nobility and madness, of the difference between a human and a beast.

And it unsettles the audience by spreading that debate beyond the two foes into the public at large — and the viewing audience beyond. How often does a big action movie ask the audience to judge a moral choice — and then offer yet another, more horrible choice?

Let me put it another way: I want to see The Dark Knight again.

The story seems simple enough. Batman (Christian Bale, reprising his role from Batman Begins) has to stop a mighty new villain. But it is almost immediately dipping into more complex territory.

While Batman has slowed crime, he has not stopped it. Gotham City is still a place laced with fear and corruption, including in the police and government. Indeed, the city's hero may not be Batman but Harvey Dent (Aaron Eckhart), the new district attorney called a ''white knight'' for his crusading attitude.

Dent's idealism by itself makes it appear he will not fit well with the vigilante Batman, but there's another complication. Dent is dating Rachel Dawes (Maggie Gyllenhaal, in the role Katie Holmes played in Batman Begins), an old love of Batman's alter ego Bruce Wayne.

And the crime-fighting goals of both Dent and Batman take a hit when the mob bosses they expect to deal with are joined by the malignant, merciless Joker.

In different hands, the Joker might well have taken over this movie. Brilliant and charismatic, he is most terrifying because he seems to believe in nothing, and so is beyond pain. The movie throws out hints about why Joker is the way he is, but they are hints that could just be myths; our only real understanding of the Joker comes from seeing what he does.

Indeed, in the first hour, the movie seems to slow when the Joker is not on-screen (and that's the one thing that keeps this from being a 4-star movie). Even then, though, the tension over what he might do next is palpable.

And screenwriter brothers Christopher and Jonathan Nolan (Christopher also directed, as he did with Batman Begins) are just setting us up for the latter stages of the movie, when the Joker's poison seeps into other characters' lives. Everyone has to make a difficult, even horrible, choice. Everyone has to suffer.

Nolan's direction is solid throughout. Bale's performance is one of the reasons I want to see this again, to watch more closely how Bale's brooding (and sorrow) are a counterweight to the Joker's flamboyance (and twisted joy).

From Batman Begins, The Dark Knight brings back Gary Oldman (as Jim Gordon, Gotham's eventual police commissioner), Morgan Freeman (as Bruce/Batman's aide Lucius Fox) and Michael Caine (as butler Alfred), and all get their moments. Gyllenhaal is an improvement over Holmes.

One reason why people like Oldman, Freeman, Caine and Gyllenhaal — not to mention Eric Roberts, as a mob boss — are important is that they know how to convey intelligence. Because, when I think about what makes The Dark Knight work, one of the things is how smart it is. Smart not just philosophically but in the details. For example, to an even greater extent than Batman Begins, The Dark Knight acknowledges the benefits a crime fighter has when he is also a billionaire.

Yes, Iron Man made a similar point, and I don't want to claim that The Dark Knight is a complete reinvention of comic-book heroics on the big screen. But it knows how to work within the form and still make things feel fresh and exciting and, yes, Oscar-worthy.

I mean, I really want to see this again.