Now in his third year at Hogwarts School of Witchcraft and Wizardry, 13-year-old Harry Potter (Daniel Radcliffe) is quickly reunited with best friends Ron (Rupert Grint) and Hermione (Emma Watson) before being alerted that trouble is, once again, afoot. Convicted murderer Sirius Black (Gary Oldman), once friends with Harry's parents before betraying them to Lord Voldemort and getting them killed, has escaped from Azkaban prison and is suspected to be heading Harry's way. Meanwhile, Harry discovers his greatest fear has taken shape in the Dementors, floating, spectral presences who are lurking around the school's premises. Although they have been sent to track down Sirius, no one is safe from the Dementors, who have the power of sucking the joy out of one's soul.

"Harry Potter and the Prisoner of Azkaban" has improved upon nearly every aspect of its predecessors, starting with its technical credits. The glorious cinematography by Michael Seresin (2003 's "The Life of David Gale") is richer and more manifestly atmospheric, bypassing the brighter tones of "Sorcerer's Stone" and "Chamber of Secrets" for colder, grayish-blue hues. The production design and art direction are more palpably sophisticated, adding texture to the exterior of the school, the secret passageways, and foreboding surrounding forests. The chamber music-inspired score by John Williams (2002's "Catch Me If You Can") builds supremely upon its now-identifiable central theme with rapturous, original new music that is less conventional and more experimental in nature.

Finally, the plentiful visual effects come close to being flawless (they are certainly the best yet in this series), seamless ly integrated into the live-action without ever drowning the narrative in a flood of CGI. Deserving special notice is the lifelike hippogriff, a half-horse, half-eagle creature who in one especially enchanting sequence takes Harry for a ride on its back through the sky and over the water. The quidditch match also feels fresh this time around by being set amidst a rainstorm and pitting Harry against the pursuing Dementors.

What works best in "Harry Potter and the Prisoner of Azkaban" is its meticulously developed, multilayered screenplay by Steven Kloves. Without giving away its many plot developments and surprises (for those who haven't read the source material), slightly off-kilter occurrences drift in and out of scenes, seemingly random and purposefully vague until their true intentions are revealed. These twists add real dimension to the proceedings, making the film worthy of multiple viewings so as to catch all of the subtle hints it dropped that one might have missed the first time around. The climax, in which Harry and Hermione find themselves traveling through their recent past in an attempt to make things right for their future—even at the risk of running into themselves—is showstopping in its levels of narrative depth and stylistic expertise, reminding slightly of the "Back to the Future" trilogy. All the while, the nightmarish Dementors hang over the proceedings, eliciting veritable dread even in the potentially mundane.

As Harry, Ron, and Hermione, Daniel Radcliffe, Rupert Grint, and Emma Watson are, by now, fully at ease and comfortable within their characters' skin and are nicely growing along with their film counterparts. Watson is especially likable and natural as the brainy, know-it-all Hermione, and she, Radcliffe, and Grint share several lovely moments together that cement the growth of their friendship in a way that was sorely missing from "Chamber of Secrets."

As Defense Against the Dark Arts teacher Professor Lupin, who has a secret tie with Sirius Black and Harry's past, David Thewlis (2003's "Timeline") is a dignified, compassionate standout. One late scene Thewlis shares with Radcliffe's Harry is particularly affecting, strengthening the silently acknowledged bond that has formed between them. As stately Albus Dumbledore, Michael Gambon (2003's "Open Range") nicely fills the shoes of the late, great Richard Harris. The rest of the recurring cast also returns, from Maggie Smith (as Professor Minerva McGonagall) to Alan Rickman (as the sniveling Professor Snape) to Robbie Coltrane (as gentle giant and now-teacher Rubeus Hagrid), but their roles are little more than extended cameos.

If "Harry Potter and the Prisoner of Azkaban" is an ideal family entertainment (albeit on e likely to be too intense and frightening for younger viewers), there is one notable drawback. As fluidly as the film moves, mixing suspense-laden action setpieces with quieter character-driven moments, very little seems to be accomplished. For the most part, Harry is physically and emotionally at the very same place at the end as he was at the beginning, and one can only hope that the clear lack of a solution to the story is merely a setup for bigger, more complicated things to come. The evolution of the story throughout a full school year has also yet to be accomplished with any noted precision in these movies; what supposedly is set over nine months seems more like the span of a week.

These hang-ups notwithstanding, "Harry Potter and the Prisoner of Azkaban" is assured, visually triumphant filmmaking that isn't simply a joy to look at, but also involves and bewitches with its tightly conceived plotting. Even with computer-generated creations filling the screen, the human ch aracters and their joys, pains, and predicaments are never overshadowed. Harry, among everything, is the star attraction, and with three motion pictures behind him the viewer has come to really care about and sympathize with him and his pals. "Harry Potter and the Prisoner of Azkaban" is happily entrancing at times, yes, but there is a genuine threat lurking around the corners that gives its every moment added weight and foreboding immediacy. As in reality. As in any good fairy tale.