In 2004, Warner Bros. released Harry Potter and the Prisoner of Azkaban. Based on the book of the same name by J.K. Rowling, it was the third movie in the series, and marked something of a turning point for the franchise as a whole, not least because of its change in director.

The Harry Potter film series began in 2001, with the first two entries being directed by Chris Columbus. For Azkaban, Mexican director Alfonso Cuarón was brought on to give Columbus a break, as the shooting schedule was so hectic. This was a big change for the franchise, as Columbus was known for writing and directing family-friendly movies like The Goonies and Home Alone. Cuarón, on the other hand, was best known for the 2001 movie Y Tu Mamá También, which is, to put it gently, not a movie you'd want to show to your kids (for your sake as much as theirs). While this might have seemed like a risky move, it actually turned out to be a good thing for the franchise, taking it in a whole new direction.

The first two films in the series, Harry Potter and the Sorcerer's Stone and Harry Potter and the Chamber of Secrets, focused on a sense of childlike wonder and served a preteen audience. They dealt with the magic of the Wizarding World, taking young viewers on a thrilling journey. This wouldn't have worked as well for the third movie, since both the cast of characters and the audience were aging. Azkaban went for a more mature tone. Magic was no longer awe-inspiring, but instead a regular part of the world these characters inhabit. While there might not be as much angst and romance as in later movie, lead characters Harry, Ron and Hermione were were now aged 13, and those things were slowly but surely starting to creep in.

The sad death of actor Richard Harris meant the role of Albus Dumbledore had to be recast. Actor Michael Gambon delivers a less gentle interpretation of the character, often pacing around irritably or shouting at students, which certainly changed the feel of Hogwarts. The movie also introduced Gary Oldman as Harry's uncle Sirius Black, who would play a central role in the fifth movie.

Caurón's influence spread into every part of the series, setting the scene for how the next five movies would look. The position of Hogwarts Castle was changed, most characters got new costumes, and he introduced a new, darker kind of humor exemplified by Aunt Marge inflating and floating away from the Dursley house in the movie's opening scenes.

Clearly, Alfonso Cuarón had a vision for what this world should look like, but on occasion he could get carried away. The monstrous Dementors are terrifying and memorable in their faceless horror, the talking shrunken heads less so. These kind of insertions hurt the worldbuilding, and seem done more for their own sake rather than because they serve any real purpose to the story.

Prisoner of Azkaban marked a tipping point for the series, not just in terms of look and feel, but also in its story, where the magical fantasy aspects began to give way to a young adult drama; the next five movies would focus on the return of Voldemort and the resulting struggle against the Dark Lord and his forces. It's interesting that this is the only movie (or book) not to feature Voldemort in any form. In fact, there's barely a mention of him, and the main "villain" is Sirius Black, a supposedly dangerous mass murderer who's escaped from Azkaban prison.

Yet Prisoner of Azkaban has become one of the most popular entries in the series, perhaps because it stands more on its own. The stakes here weren't as high, and while the whole school was in some state of paranoia over Black's escape, there's no sense that the entire Wizarding World is at risk, or even that Hogwarts may have to close, as was the case in Chamber of Secrets. This let the story play out more like a standard boarding school or high school movie, where Harry's biggest concern was whether he'd get to go on a trip to Hogsmeade, and a lot of the story was taken up with things like Quidditch matches and sneaking through secret passages.

All of this made Prisoner of Azkaban the perfect vehicle to change up the series. It provided some breathing space for the audience before the reintroduction of Voldemort, and eased them into the darker tone of Goblet of Fire. The changes essentially amounted to a soft reboot of the franchise, and while it might have been Chris Columbus who first brought the world to the screen, Alfonso Cuarón's vision for it is arguably more influential.