It’s difficult to separate the movie from its mystique. Even under ordinary circumstances, The Dark Knight would have been one of the most hotly awaited movies of the summer blockbuster season. The loss of Heath Ledger to an accidental prescription-drug overdose in January has amplified the buzz around the film — and his crazed performance as the Joker — to extraordinary levels.

Nothing could possibly satisfy that kind of expectation. The Dark Knight comes pretty close.

Christopher Nolan’s film is indeed an epic that will leave you staggering from the theater, stunned by its scope and complexity. It’s also, thankfully, a vast improvement over his self-serious origin story, 2005’s Batman Begins.

As director and co-writer with his brother, Jonathan (David S. Goyer shares a story credit), Nolan has found a way to mix in some fun with his philosophizing. Ambitious, ex­plosive set pieces share screen time with meaty debates about good versus evil and the nature of — and need for — a hero.

Batman (Christian Bale) has been that guy. Now, he’s not so sure he should be anymore. He’s protected Gotham fiercely (and with some fierce toys), but the new district attorney, Har­vey Dent (Aaron Eckhart), seems to be putting a dent in organized crime with help from Lt. Gordon (Gary Oldman). Perhaps Batman should return to his “normal” life as billionaire Bruce Wayne and leave the cleanup work to the professionals. Maybe he can even rekindle his romance with old flame Rachel Dawes (Maggie Gyllen­haal, taking over more than capably for Katie Holmes, although she doesn’t get much to do, either).

And so The Dark Knight presents an existential crisis — what comic-book hero doesn’t suffer these? — but does so in a totally different way from its predecessor. Whereas Batman Begins felt too solemn and introspective, this installment might actually be too fast. Like the Caped Crusader himself, speeding through the streets of Gotham City on his tricked-out Bat-Pod motorcycle, Nolan moves breathlessly from one scene to the next.

Trouble is, he’s got such great vision and is so adept at creating a compelling mood, it makes you wish he’d held some moments for a beat or two longer, just to savor them — and to let us do the same. A couple of scenes in Bruce’s stark, crisply lit Bat-bunker come to mind, as does Bat­man’s nighttime flight over a glittering Hong Kong. (Wally Pfister, a longtime Nolan collaborator who also shot Bat­man Begins and Memento, returns as cinematographer. Hans Zimmer and James Newton Howard once again teamed up to compose the huge, sweeping score.)

Nolan was wise enough, however, to give Ledger plenty of room to shine — albeit in the actor’s indelibly perverse, twisted way. There’s nothing cartoony about his Joker. Ledger wrested the role from previous performers Cesar Romero and Jack Nicholson and reinvented it completely.

Yes, he’s funny, wringing laughs from both clever one-liners and maniacally grand schemes. He can be playful, finding unexpected avenues into the character: “You complete me,” he purrs to Batman.

But because there’s no logic behind his mayhem, he’s also truly terrifying. The terror he inflicts on Gotham is meticulously planned (the opening bank heist, shot with IMAX cameras, is a marvel of timing) and yet his sole inspiration is to create chaos, then watch the city squirm and burn.

That his attacks grow larger each time, regardless of the collateral damage, makes him so genuinely disturbing. Ledger seems to have understood that, and brings an appropriate — and riveting — unpredictability to the role. It’s also a neat touch that his makeup, which looked like a slapdash effort from the start, steadily deteriorates, streaking, cracking and peeling away as the film progresses; it’s an outward manifestation of his psychological spiral.

Bale seems more assured than ever, now that he has more facets of Batman/Bruce’s personality to reveal than he did in the last film. He’s consistently proven he’s capable of going to dark, scary places for his characters.

Also returning are Michael Caine as Bruce’s butler, Alfred, and Morgan Freeman as gadget guru Lucius Fox. Both veterans help anchor the movie with a wisdom and calmness when everything (and everyone) is in a state of turmoil.

Batman and the Joker’s relationship is one that’s strangely symbiotic — you could even call it codependent. Or as the Joker puts it, “You and I could do this forever.”

If only.

The Dark Knight

*** 1/2

Rated PG-13, 152 minutes.
Opens Friday.