Will chaos and fear reign in Gotham City? That's one question posed in Christopher Nolan's The Dark Knight, a profoundly disturbing study of how terror can destabilize individuals and whole societies. Although the stunning action sequences derive from a traditional superhero plot, this chilling film is more sophisticated crime drama than special effects extravaganza. The ideas are as memorable as the brilliant spectacle.

At least two characters are tagged as "dark knights" and the movie amounts to a long, bleak night with only the faintest rays of sunlight peaking through at the end. Heath Ledger's Joker, a fiendish knave for the ages, wreaks havoc by igniting a battle for the souls of these two conflicted figures. They are Batman -- portrayed as in Nolan's Batman Begins by Christian Bale – and the zealous young district attorney Harvey Dent, played by Aaron Eckhart. Their Manichean struggle to find a balance between their own noble and base instincts is entwined with a contest for the soul of the metropolis itself.

Tormented crime-fighters have ably filled movie screens this summer. Iron Man, The Incredible Hulk, Hellboy, and Hancock are all divided against themselves. But in the cases of Batman and Dent, this fundamental superhero tension is explored with a rare depth and attention to its political implications. With the help of Lt. Gordon (Gary Oldman), Alfred (Michael Caine), and Lucius Fox (Morgan Freeman), they endeavor to uphold justice while avoiding crossing the line into a kind of fascistic elitism. Their exceptional abilities and accomplishments put them in a potentially messianic position littered with pitfalls.

A syndicate of multi-ethnic gangs is running rampant in Gotham City. Batman and Gordon, head of the major crimes unit, plan to seize the mobsters' ill-gotten lucre.  Before they get the chance however, the criminals' Hong Kong colleague takes their pooled cash out of the country, leading Batman to kidnap him and bring him back to Gotham. The Joker then steps in and assures the bosses that he'll get their money back and, in the process, kill Batman. Public opinion has already started to turn against the Caped Crusader and Bruce Wayne believes it's time to find a successor -- someone to provide the citizenry with a new vision of hope and justice. Dent might fit the bill.

Unfortunately, no one is prepared for the fiendish campaign of terror unleashed by the Joker, armed with an array of pyrotechnic devices, greasy hair, sweat-smudged make-up, and a reedy voice. He blackmails Batman by announcing that more people will die if he doesn't reveal his identity. Then, with maniacal ingenuity, he uses Rachel Dawes (Maggie Gyllenhal) -- Bruce Wayne's ex and Dent's fiancé -- to force a literal and figurative fissure in Dent's identity and push Batman to the brink of becoming a force of evil himself.

The Joker's motives for conducting his sadistic social experiment are pure: he disrupts the city's equilibrium by killing and maiming with no goal other than the pleasure of fomenting chaos. As Alfred puts it, "Some men just want to watch the world burn." Even if Ledger hadn't died earlier this year, his sublimely wicked performance would generate Oscar buzz. Taking in every overt and nuanced dimension of the character he creates is enough to make The Dark Knight a great film.

Yet Nolan goes much further, extending the defining motif of noble vigilantism that he broached in Batman Begins by asking how one responds to such unbridled amorality. Do you fight brutality with brutality, ignore conventional boundaries between right and wrong and adopt equally warped methods? Do you exploit fear with the same cynicism as your enemy? The Dark Knight asks hard, relevant questions about the ethics of leadership in desperate times.

Some will see it as a cautionary tale concerning the psychology of fear (drawing parallels with the Patriot Act and the Bush Administration's tactics following 9/11) and others will interpret it as an endorsement of a certain authoritarian license that those in power must wield in order to be effective. Every superhero movie boils down to the angels and demons within the individual. Few have been this elegant, this steely, this riveting -- boasting a visual splendor that matches its trenchant themes and inspired performances. 

(Released by Warner Bros. and rated "PG-13" for intense sequences of violence and some menace.)