Every Harry Potter movie has the same plot. The young wizard (Daniel Radcliffe) struggles in the world of muggles (that's normal people), gets transported to wizarding school Hogwarts, where an evil threat is brewing, bonds with buddies Ron (Rupert Grint) and Hermione (Emma Watson), feuds with snotty classmate Draco Malfoy (Tom Felton), and eventually defeats the evil whatever while maturing a bit.
The third installment, Harry Potter and the Prisoner of Azkaban, deviates only slightly from the formula established by its two predecessors, but its thematic and stylistic changes make all the difference. Harry starts the film once again back at home with his nasty aunt, uncle and cousin, but is quickly whisked off to Hogwarts to begin his third year. There he learns that the nefarious Sirius Black (an underused Gary Oldman) has escaped from Azkaban, a mystical prison. Black was a close associate of Lord Voldemort, the uber-baddie who killed Harry's parents and left the youngster with the lightning bolt-shaped scar on his forehead. Even worse, Black was a good friend of Harry's parents until selling them out to their arch-nemesis.
Naturally, Black is out to kill Harry, who, well used to that sort of thing, takes it rather in stride. All the usual suspects are back at Hogwarts, including kind Prof. McGonagall (Maggie Smith), insidious but well-intentioned Prof. Snape (Alan Rickman), giant and warm-hearted groundskeeper Hagrid (Robbie Coltrane), now promoted to professor himself, and headmaster Albus Dumbledore (Michael Gambon, ably replacing the late Richard Harris). So many of those suspects are back, actually, that many of them get barely a moment of screen time and a line or two, as the source novels by J.K. Rowling just get longer and longer as the series goes on.
Time is made for some new faces, including the traditional new Defense Against the Dark Arts teacher, Prof. Lupin (David Thewlis) and loopy divination teacher Prof. Trelawney (Emma Thompson, barely recognizable in Coke-bottle glasses and frizzy hair). Somehow new director Alfonso Cuarón, taking over for Chris Columbus, manages to balance them all, and while fans of the book may be disappointed that some of their favorite characters get the short shrift, the film makes even the most minor figures seem important.
With Black on the loose, the school is overrun by dementors, creepy, wraith-like creatures who serve as the guardians of Azkaban but are still dangerous to law-abiding wizards. Prof. Lupin takes Harry under his wing, teaching the boy charms to fend off the dementors and helping him come to terms with the loss of his parents. Now 13, the central trio start to show hints of adolescence, and Ron and Hermione share a few moments that hint at future romance (Harry himself is set to develop a crush on a fellow student in the fourth installment).
Azkaban still follows Potter mythology closely: Author Rowling is heavily involved, and both screenwriter Steve Kloves and director Columbus (as producer) remain as guiding forces from the first two films. But Cuarón takes the story's darker tone and expands it, with a real sense of menace to the threat of Black, and especially the thoroughly creepy dementors. Nearly every scene takes place at night or under gloomy cloud cover, and Cuarón imbues Hogwarts itself with a slightly unsettling gothic vibe.
Although his last project was the graphic coming-of-age drama Y Tu Mama Tambien, the Mexican Cuarón is actually an inspired choice for the Potter franchise. His previous English-language films include a lush, if slightly empty, adaptation of Great Expectations, with Ethan Hawke and Gwyneth Paltrow, and the acclaimed children's fable, A Little Princess, also a literary translation. He brings a sense of wonder that the bland, populist Columbus often missed, as well as a slightly more showy style. In general, Cuarón's Hogwarts feels more real, as he throws in scenes of Harry and Ron just sitting around their dorm, and the central trio spend much of the film in modern dress, not the old-fashioned wizards' robes of the earlier movies.
Even within the familiar formula, Azkaban holds its share of surprises, and the ending doesn't tie everything up as neatly as you'd expect. The three leads, growing up under a microscope as many child stars before them, acquit themselves very well given the more complex emotions they are called upon to portray. Watson in particular does a solid job of showing Hermione's darker side. The supporting cast, a who's-who of British actors, offers impeccable support, and Gambon brings his own flair to Dumbledore without stepping on Harris' memory.
It's a shame that Cuarón has yielded the next installment to workman-like director Mike Newell, whose resume is both stylistically and qualitatively inconsistent. In this outing, at least, Cuarón finds the perfect balance of individual style and faithful representation, darkness and light entertainment, and delivers the strongest installment in the Potter series so far.