It would make sense that, as young wizard-in-training Harry Potter and his classmates increase in age, the series they are in would mature along with them. And so it is with "Harry Potter and the Goblet of Fire," the fourth—and so far, best—film adaptation of writer J.K. Rowling's rapturously popular seven-part fantasy opus. Marvelously directed by Mike Newell (2003's "Mona Lisa Smile"), the film smoothly and economically translates the monstrous 734-page novel into 157 minutes that effortlessly fly right by while capturing an appropriately epic feel. More than that, though, "Harry Potter and the Goblet of Fire" is the series' most complete and satisfying entry to date on all counts—the most complex, the most humane, the most involving, the most creatively eclectic, the most threatening, the largest in scope, and, coincidentally, the most emotionally intimate.

Plagued by obscure nightmares about the mysterious Lord Voldemort (Ralph Fiennes), 14-year-old Harry Potter experiences another harbinger of doom while attending the Quidditch World Cup. After the camp site for the event is ransacked and burned to the ground by rampaging Death Eaters, Harry witnesses The Dark Mark scrolled in the sky—a symbol of Lord Voldemort's menace.

Soon after, Harry and best friends Ron Weasley (Rupert Grint) and Hermione Granger (Emma Watson) are back at Hogwarts School of Witchcraft and Wizardry for another year. This time, Hogwarts is hosting the yearlong TriWizard Tournament, a death-defying trio of tasks which one chosen student from each school of magic—the other two are Beauxbatons and Durmstrang—compete in. Although the rules state that the competitor must be seventeen, Harry's name miraculously comes up when the Goblet of Fire picks the players. Many of his classmates, including a feeling-betrayed Ron, believe that he cheated by putting his name in the drawing, but he is just as at a loss for who did enter him as anyone. Nonetheless, Harry has no choice but to press forward with a series of three challenges as difficult and dangerous as anything he has ever faced before. What he does not yet know is that an even bigger threat is inching closer to him in the form of his parents' murderer, Lord Voldemort.

"Harry Potter and the Goblet of Fire" is the first in the series to earn a PG-13 rating, but the tougher rating is fitting to match the escalating stakes Harry must face as he grows from a boy into a man. Director Mike Newell and returning screenwriter Steve Kloves (2000's "Wonder Boys") stay truthful to the more foreboding tone of the novel even when they must condense or excise a lot of material to fit into a two-and-a-half-hour running time, and their hard work is destined to not only please, but also mesmerize, both fans of the books and Muggles alike.

Seamlessly plotted and constructed, the film takes a further step toward transitioning from an all-in-fun family movie into a legitimately serious and distinguished dramatic fantasy saga destined to go down in cinematic history. The three centerpiece set-pieces as Harry competes in the competition—a dragon battle to retrieve a golden egg; an underwater rescue complete with nasty sea creatures, and a journey through a foggy, perilous hedge maze to reach the prized TriWizard Cup—are visually astounding, at times scary, and thoroughly exciting. British director Newell, not exactly known for his expertise in action sequences, knows exactly how to build these scenes with taut suspense without losing sight of the human drama that Harry is facing along the way. Only the last task involving the maze could have been improved with some extensions; as is, it is over too soon and doesn't quite reach the height of its crafty ambitions. Fortunately, this minor disappointment is rectified soon after as Harry comes face-to-face with Lord Voldemort for the first time. It is a ghastly, riveting, and potentially iconic moment to rival Luke Skywalker's discovery that Darth Vader is his father at the end of 1980's "The Empire Strikes Back."

These scenes are superb examples of technical craftsmanship, yes, but they would be nothing without an enthralling narrative and essential human element. This is where "Harry Potter and the Goblet of Fire" excels and surpasses its predecessors. Just as absorbing, if not more so, than the TriWizard Tournament are the growing pains teenagers Harry, Ron and Hermione are going through as they grapple with remaining close friends even as their hormones go wild. The joys, the disappointments, the inexperience in dealing romantically with the opposite sex—it is all here, treated with a painful, bittersweet authenticity that recalls John Hughes' 1980s works.

Meanwhile, the three protagonists face their first real conflicts with each other that go far beyond jokey childish banter, acting as an invaluable counterbalance to the more dire dangers in Harry's life and strengthening their complicated relationships with each other to a three-dimensional level. The material involving the school's Yule Ball, a Christmas Eve-held boy-girl dance, is beautifully done and ultimately poignant, with Harry's, Ron's and Hermione's fairy tale hopes not turning out quite as they expect.

By now, the performances from Daniel Radcliffe, Emma Watson and Rupert Grint fit like well-worn gloves with their roles. Radcliffe, who began a little rough around the edges and kind of bland in 2001's "Harry Potter and the Sorcerer's Stone," has grown leaps and bounds as an actor able to convey a wide range of multifaceted emotions. He is the consummate movie hero—likable, resourceful, capable of strength even at his darkest moments, deserving of happiness, and flawed. The same things could be said for Watson, delightfully warm and vulnerable as Hermione, and Grint, who has never been better or used quite as well, as Ron. More than the other two, Grint comes into his own here in eye-opening ways, for the first time moving away from being just comic relief and into a full-fledged human being with valid insecurities and resentments. There is a richness to these characters, and to many of the supporting ones, that become all the more evident with each film.

Welcome new faces to the series include Miranda Richardson (2004's "The Phantom of the Opera"), energetic and with a keen sense of comic timing as constantly-embellishing tabloid reporter Rita Skeeter; Brendan Gleeson (2005's "Kingdom of Heaven"), memorably quirky as new Hogwarts instructor Mad-Eye Moody; Frances de la Tour, a formidable presence as giant headmistress of the Beauxbatons Madame Maxine, who starts a relationship with Hagrid (Robbie Coltrane); newcomer Katie Leung, innately sweet as Harry's object of affection, Cho Chang, and Ralph Fiennes, suitably freaky and intense in the vital key role of villain Lord Voldemort. Previous minor characters from the other pictures also see their parts expanded, including Ron's younger sister, Ginny (Bonnie Wright), and classmate Neville Longbottom (Matthew Lewis), who helps Harry in a moment of need.

Artistically without fault, from the sumptuously accomplished cinematography by Roger Pratt (2004's "Troy"), to the top-notch visual effects work, to the production design by Stuart Craig (2000's "The Legend of Bagger Vance") that paints Hogwarts with a hint more realism than before without forgetting its fantastical layers, "Harry Potter and the Goblet of Fire" is an extravagant entertainment that makes a return to the sort of "event" moviegoing experience that doesn't seem to come around as often anymore. What makes the film special is not its effects and action, however, but the intelligence and naturalism in which the story is told and the characters depicted.

Far closer to a highly charged thriller than a kid pic this time, there is also an urgency and mounting sense of dread hanging over the proceedings that only raises one's full involvement in what is going to happen to these beloved characters, both now and in the future. When Hermione says to Harry and Ron in the exquisitely played-out last scene, "Everything's going to change now, isn't it?" there is a level of heartbreaking pathos in her statement that blindsides the viewer with its power and subtext. She's not just referring to the evil forces now surrounding them, but in terms of their friendship, coming-of-age and inevitably expanding their horizons outside of the tight-knit bond they have formed over the last four years. For Harry Potter, the process of growing up may be the hardest task of all.