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Harry Potter and

Alfonso Cuarón just couldn’t resist: In the opening scene of Harry Potter and the Prisoner of Azkaban, the Mexican director’s Peeping Tom camera discovers the now-13-year-old wiz kid huddled under his covers ’round midnight, playing with his magic wand. There are great explosions of house-rattling light, and Harry flashes a guilty grin at his naughtiness. Then the teen can’t help but do it again. Young followers of J.K. Rowling’s best-selling series will no doubt think, Hey, that’s not what happened in the book. And adult fans of Cuarón’s sweet but soft-core 2001 film, Y Tu Mamá También—about two adolescents exploring their budding sexuality—will squirm and think, Uh-oh…

Now, now: In the latest and by far best Harry Potter movie, the Boy Who Lived is still more interested in boggarts than boobies. It really is just a magic wand he’s fiddling with (for now). But from that wink-wink preface—and the following scene, in which Harry pulls a Carrie-esque tantrum in his Uncle Vernon and Aunt Petunia’s suburban London kitchen after his dead mother is called a “bitch”—it’s obvious that Hollywood überhack Chris (Home Alone) Columbus, who directed the first two Potter films, is no longer calling the shots. His adaptations were pretty but safe, heavy on the FX and lite on the drama. And there certainly wasn’t anything open to interpretation or, for that matter, imagination in his clean, candy-colored work.

Given his rep as a sex-friendly filmmaker, Cuarón was a curious choice to be put in charge of the pivotal third installment in this blockbuster kiddie franchise. But the 42-year-old director manages a feat Columbus never came close to pulling off: He delivers a dark, engrossing thriller that not only is absolutely gorgeous to gawk at but also deftly captures the complexities of Rowling’s adolescents-in-wonderland world, all the while staying faithful to her story.

It helps that the bazillionaire author’s third book was the first in the series to have teeth to it. Much-plagued Harry (here-comes-puberty Daniel Radcliffe, all lanky frame and budding handsomeness) is on the lookout for nasty grown-up Sirius Black, a recent escapee from the titular prison and the man who supposedly helped chief baddie Voldemort murder Harry’s parents. Black is played by Gary Oldman, and when we first see him, he is wailing (as only Oldman can) within the animated confines of newspapers and wanted posters, which Cuarón places at the edges of his carefully constructed frames in a nifty bit of trickery that disorients as much as it distracts. (It’s akin to Ridley Scott’s fuzzing out the dialogue in Alien—audience unease is the key.) For Harry and loyal chums Ron Weasley (increasingly dorky Rupert Grint) and Hermione Granger (increasingly charming Emma Watson), Black is their most terrifying foe yet, mainly because he’s not a ghost or a ghoul but a human, just like them.

Although Azkaban is loaded with laughs—a connecting thread of the Whomping Willow wreaking evil-tree havoc in fall, winter, and spring gives the movie a fast-paced fluidity and is hilarious to boot—it also has several spill-your-popcorn scares. Whether he’s setting the action in real-world London, at the Gothic Hogwarts School of Witchcraft and Wizardry, or in the Dickens Village–gone–to–seed town of Hogsmeade, Cuarón bleaches all happy-shiny hues from the film, making each locale a haunted landscape in whites, blacks, and browns. (There is a quick trip through a sweets shop—ah, innocence—but the Bertie Bott’s Every Flavor Beans are not nearly as red as the pustules seen earlier on the Knight Bus driver’s neck.) The lack of brightness contributes to a constantly creepy vibe, and the murky nature of things allows such computer-generated monsters as the soul-sucking dementors—the Grim Reaper-esque guards searching for Black and messing with our hero—to look even more menacing. There’s also a don’t-look-under-the-bed jolt involving The Monster Books of Monsters. (You have to stroke its spine.) And even that pissant

Malfoy kid (Tom Felton) looks

more psychotic.

Of course, this being a Harry Potter movie, there are plenty of less spooky wonderments, as well. The obligatory Quidditch match (basically sky-high field hockey on rocket-boosted broomsticks, for all you unknowing Muggles) is set in a rainstorm and finally looks fantastic. Harry takes a majestic ride on Buckbeak the hippogriff, a half-eagle, half-horse in gentle giant Hagrid’s (Robbie Coltrane) stable; as the winged beastie soars over mountains and swoops low to a lake, Harry sees his reflection in the light-kissed water, and you can’t help but get a tingly summer-matinee feeling in your belly.

And in the movie’s best set piece, new Defense Against the Dark Arts teacher Remus Lupin (David Thewlis, as the series’ first multidimensional adult character) lines up his students to face off against a boggart, a nasty phantasm that takes the shape of your worst fear—until you manage to turn it into your funniest thought. At this point, Cuarón ditches John Williams’ saccharine score, which Columbus smeared all over his flicks, for a snappy bit of jazz, and the lesson grooves along as the kids, one by one, turn nightmares (a giant spider) into dreams (a giant spider on roller skates).

No matter how spectacular things get, Cuarón always make sure that story takes precedence over scenery—which is not to say he doesn’t style it up with the best of ’em. (After all, the acting is good—Alan Rickman as Potions Professor Snape—but it’s not that good—nondescript Michael Gambon, replacing the late, great Richard Harris as Dumbledore.) His camera is an acrobatic marvel, especially in the movie’s extended finale, when Harry, Ron, and Hermione meet up with Black, and a chase through the woods, involving a werewolf and a fleet of dementors, jerks and dips like a roller coaster. The kids also do a bit of time-warping, and the director bookends the back-to-the-future turn with slow, ponderous journeys through the workings of a clock.

Unfortunately, Cuarón won’t be directing the fourth Potter movie; Four Weddings and a Funeral’s Mike Newell is signed up for that one. But here’s hoping he comes back on for the fifth, Harry Potter and the Order of the Phoenix, which is all about Harry’s frustrations with the world of teen-age girls. Lord knows what Cuarón would have Harry playing with under the sheets in that one. CP