To be honest, I’ve never really gotten the big deal about Harry Potter or why people would stand outside bookstores waiting to buy the latest book—never mind why fans would dress up like their favorite characters for the opening of the newest film. After seeing the third installment, "Harry Potter and the Prisoner of Azkaban," I still don’t understand fans’ behavior, but I do know a great movie when I see it—and this is the best Potter film yet. Daniel Radcliffe, who definitely has grown up since he debuted as Harry Potter in 2000, has returned as Harry for another year at Hogwarts School of Witchcraft and Wizardry, along with pals Hermione (Emma Watson) and Ron Weasley (Rupert Grint). The friends have barely gotten a chance to catch up on their summers when they learn that the infamous murderer Sirius Black (Gary Oldman, "Sin") is on the loose and may be looking to make Harry his next victim. The previous Harry Potter films, "Harry Potter and the Sorcerer’s Stone" and "Harry Potter and the Chamber of Secrets," were both very entertaining films, but "Prisoner" ironically feels much more unrestrained by the pressure of translating J.K. Rowlings’ novels into films and is easier to just enjoy as a movie. While I could look objectively at the first two films and appreciate them for being enjoyable, if not particularly memorable, the "Prisoner" packs more thrills and scenes that had me thinking, "Man, that was cool!" Director Alfonso Cuaron ("The Children of Men"), new to the Harry Potter scene, creates a great balance between making the light moments funny, the more intense moments scary and unnerving, and the characters’ highs and lows more engaging. As with any Potter installment, part of the fun is in meeting the new Defense Against the Dark Arts teacher, this year taught by the refined Professor Lupin (David Thewlis, "Timeline"). The main characters also start taking Divination, taught by the very weird Sybill Trelawney (Emma Thompson, "Love Actually"). One of the unusual new cast additions are the creepy Dementors, visually impressive creatures who bear more than a passing resemblance to the Lord of the Ring film villain Ringwraiths. Still, you can never go wrong by cloaking an intimidating character in long, tattered black robes and giving them indistinguishable faces—even if they’re sure to be the cause of more than a few children’s nightmares. The Dementors help provide an element missing in the previous Potter films—entities whose motivations, whether good or evil, remain a mystery throughout the film. Michael Gambon ("Standing Room Only") assumes the role of Dumbledore, played with such presence by the late Richard Harris. Similar to Mary Alice, who had to take over the late Gloria Foster’s role of Oracle in "The Matrix Revolutions," Gambon has the unenviable task of replacing an actor that has already been established in the film mythos as that particular character. As the Potter saga continues, Cuaron gets to tease at slight romantic tension between Hermione and Ron, with Watson and Grint once again providing the perfect team for Radcliffe. While they may no longer be cute little kids running around on adventures, they have become the faces for the characters and have made the roles their own. With a running time of two hours plus, "Prisoner of Azkaban," like its predecessors, probably runs too long for a film with a target base largely comprising 7 to 12 year olds. One gripe is that screenwriter Steve Kloves assumes that the entire audience is familiar with the story and the rush of characters, especially in the beginning, may prove a bit overwhelming to Potter novices. These days, it’s rare when a sequel manages to capture any of the excitement that made the first one so memorable—which makes it even more surprising that "Prisoner" is the best Harry Potter film yet.