From left, Rupert Grint as Ron Weasley, Emma Watson as Hermione Granger and Daniel Radcliffe as Harry Potter star in "The Prisoner of Azkaban." Warner Bros.

But the 13-year-old wizard is too wrapped up in conversation to notice — an escaped psychopath named Sirius Black is out to kill him, after all.

This is the increasingly sinister world of "Harry Potter and the Prisoner of Azkaban," the third movie based on author J.K. Rowling's phenomenally popular books.

Harry is another year older, and a little more cynical and wiser after facing down two incarnations of his nemesis, the warlock Voldemort, in the previous movies.

The orphan boy is also somewhat embittered by his lonely lot in life, and tired of dealing with villains and monsters — not to mention school bullies.

One major change is the movie's director.

Alfonso Cuaron, who made the 1995 children's film "A Little Princess" and the very different 2001 adult coming-of-age tale "Y Tu Mama Tambien," took over the filmmaking duties from Chris Columbus, who made the previous Potter movies and such cheery family films as "Home Alone" and "Mrs. Doubtfire."

Cuaron said he aimed for a more sophisticated "Harry Potter" story — a children's movie with metaphor and subtext about the melancholy of growing up.

"A big theme of this film is time, in the sense of what you leave behind and what you travel to," the director said. "It's about acceptance, and acceptance comes with time — or the right understanding of time."

That theme is even represented throughout the set design with the repeated use of timepieces.

When Harry's annoying Uncle Vernon gets angry, a cuckoo clock seems to mock him. Characters survey the grounds of Hogwarts School of Witchcraft and Wizardry from the glass face of a gigantic clock tower, while important moments play out beneath a humongous pendulum. And Harry's pal Hermione seems to have a device that beats time by allowing her to be in two different classes at once.

And while the previous movies — "Harry Potter and the Sorcerer's Stone" and "Harry Potter and the Chamber of Secrets" — were more linear tales, "Prisoner of Azkaban" literally doubles back on itself, with the climax viewed twice from different perspectives.

The movie is already regarded as superior to its predecessors, but Cuaron's change of tone was a risk that could have aggravated the longtime fans of Rowling's prose.

Steve Kloves, the screenwriter who has adapted all of the "Harry Potter" movies, said the director had to balance his own wishes with the requirements of the series.

"Alfonso will tell you that he inherited a glorious world, an incredible paint box to play with. And what he did was, he chose his own colors," Kloves said. "I think the world is recognizable, it's just been given a bit of a darker cast, which reflects the story and what Harry is going through emotionally."

The last movies were big hits. Critics complained they were too literally adapted from the books, but fans generally loved the faithfulness to Rowling's stories.

Cuaron said he didn't want change for the sake of change, but felt "Harry Potter" could use some tweaks. "Every director is a different mind, and I had my own approach — for good or ill," he said.

The characters wear modern street clothes for much of the movie, instead of the flowing school-uniform robes seen so often in the previous films. But before he could make even that change, he had to consult with a higher power.

"That had to do with conversations with Jo Rowling," Cuaron said. "She said, `Yes, for me the cloaks and everything makes sense for the academic time but in personal time they would be wearing their own clothes."'

He also made the school and its grounds look more worn and earthy — as if they'd been battered for hundreds of years by misplaced adolescent magic — and he favored an iris effect for ending scenes, with perspective dimming to a single point before opening again, to give "Azkaban" a silent-movie feel.

Cuaron stepped in after Columbus said the rapid production schedule was too much for one filmmaker to maintain as Warner Bros. raced to produce as many "Harry Potter" movies as quickly as possible before its child stars grew up.

Daniel Radcliffe, Rupert Grint and Emma Watson — who play Harry and his pals Ron and Hermione, respectively — are already at work on the fourth movie "Harry Potter and the Goblet of Fire" with yet another director, "Four Weddings and Funeral" filmmaker Mike Newell.

Radcliffe, now 14, said Cuaron didn't shy away from the bleak touches that showed magic has a dangerous side. For instance, Potter fans are familiar with the Whomping Willow, the limb-swinging living tree that battered a flying car in the second movie — but are they prepared to see it whack sweet little bluebirds into puffs of falling feathers?

"There's slightly more twisted humor in it, which I always love — I've got quite a black sense of humor," Radcliffe said.

The maturity of the child stars was another factor that gives depth to the new movie, Radcliffe added.

A hallmark of the Harry Potter stories is the hero's lost innocence. The boy, whose parents were murdered by Lord Voldemort, has been burdened repeatedly by sadness and responsibility that only intensifies in the later books. The film version of "Azkaban" marks a turning point in Potter's fleeting youth.

"Harry's finding his own fingerprints," Kloves said. "In this story he meets two people who knew his parents intimately and are both haunted by their deaths in the way Harry is."

Those characters: kindly Professor Lupin (David Thewlis), the new Defense Against the Dark Arts teacher who has a hairy secret, and Sirius Black (Gary Oldman) the reputed madman accused of leading Potter's parents to their doom.

Another change was thrust upon the makers of "Azkaban" — the 2002 death of Richard Harris, who played the wise Hogwarts headmaster Dumbledore.

Michael Gambon stepped into the character's flowing white beard, portraying Dumbledore as a "a little goofier," Cuaron said.

"Dumbledore rarely makes speeches or says anything serious. Everything is very oblique and almost bizarre," the director said. "Obviously he knows everything. He just pretends to be this oddball, this fool."

He said he could not ask Gambon to do an "impression" of Harris to make the transition completely seamless.

"But he is stepping into this with a lot of respect for how Dumbledore was played in the past," Cuaron said. "He even kept a little Irish twist to his accent in a nod to Richard Harris."

Associated Press Writer Rebecca Miller in New York contributed to this story.