Harry Potter (Daniel Radcliffe) has been spending another dissatisfying summer with the Dursleys. When Aunt Marge Dursley (Pam Ferris) insults his parents, he loses his temper and accidentally causes her to inflate like a balloon and float away. Fed up, Harry then flees the Dursleys with his luggage. The Knight Bus arrives and takes Harry to the Leaky Cauldron, where he is pardoned by Minister of Magic Cornelius Fudge (Robert Hardy) for using magic outside of Hogwarts. After reuniting with his best friends Ron Weasley (Rupert Grint) and Hermione Granger (Emma Watson), Harry learns that Sirius Black (Gary Oldman), a convicted supporter of the dark wizard Lord Voldemort, has escaped Azkaban prison and intends to kill him.
The trio return to Hogwarts for the school year on the Hogwarts Express, only for dementors to suddenly board the train, searching for Sirius. One enters the trio’s compartment, causing Harry to pass out, but new Defence Against the Dark Arts teacher Professor Lupin (David Thewlis) repels the dementor with a Patronus Charm. At Hogwarts, headmaster Albus Dumbledore announces that dementors will be guarding the school while Sirius is at large. Hogwarts groundskeeper Rubeus Hagrid (Robbie Coltrane) is announced as the new Care of Magical Creatures teacher; his first class goes awry when Draco Malfoy (Tom Felton) deliberately provokes the hippogriff Buckbeak, who attacks him. Draco exaggerates his injury, and his father Lucius Malfoy (Jason Issacs) later has Buckbeak sentenced to death.
The Fat Lady’s (Dawn French) portrait, which guards the Gryffindor quarters, is found ruined and empty. Terrified and hiding in another painting, she tells Dumbledore (Michael Gambon) that Sirius has entered the castle. During a stormy Quidditch match against Hufflepuff, dementors attack Harry, causing him to fall off his broomstick, which lands at Whomping Willow, where it is destroyed. At Hogsmeade, Harry is shocked to learn that not only had Sirius been his father’s best friend and apparently betrayed them to Voldemort, but is also Harry’s godfather. Lupin privately teaches Harry to defend himself against dementors, using the Patronus Charm.
After Harry, Ron, and Hermione witness Buckbeak’s execution, Ron’s pet rat Scabbers bites him and escapes. When Ron gives chase, a large dog appears and drags both Ron and Scabbers into a hole at the Whomping Willow’s base. This leads the trio to an underground passage to the Shrieking Shack, where they discover that the dog is actually Sirius, who is an Animagus. Lupin arrives and embraces Sirius as an old friend. He admits to being a werewolf, and explains that Sirius is innocent. Sirius was falsely accused of betraying the Potters to Voldemort, as well as murdering twelve Muggles and their mutual friend, Peter Pettigrew. It is revealed that Scabbers is actually Pettigrew (Timothy Spall), an Animagus who betrayed the Potters and committed the murders.
Severus Snape arrives to apprehend Black but Harry knocks him unconscious with the Expelliarmus charm. After forcing Pettigrew back into human form, Lupin and Sirius prepare to kill him, but Harry convinces them to turn Pettigrew over to the dementors.
As the group departs, the full moon rises and Lupin transforms into a werewolf. Sirius transforms into his dog form to fight him off. In the midst of the chaos, Pettigrew transforms back into a rat and escapes. Harry and Sirius are attacked by dementors, and Harry sees a figure in the distance save them by casting a powerful Patronus spell. He believes the mysterious figure is his deceased father before passing out. He awakens to discover that Sirius has been captured and sentenced to the Dementor’s Kiss.
Acting on Dumbledore’s advice, Harry and Hermione travel back in time with Hermione’s Time Turner, and watch themselves and Ron repeat the night’s events. They save Buckbeak from execution and witness the Dementors overpower Harry and Sirius. The present Harry realises that it was actually him who conjured the Patronus, and does so again. Harry and Hermione rescue Sirius, who escapes with Buckbeak. Exposed as a werewolf, Lupin resigns from teaching to prevent an uproar from parents. He also returns the Marauder’s Map to Harry, as he no longer has the authority to confiscate contraband. Sirius sends Harry a Firebolt broom, and he happily takes it for a ride.
I remember going to the midnight premier with my mom to see this film. I admit my entire childhood from 1st grade and up was being a major fan of Harry Potter (and Disney) but HP is something both my parents got into as well. Now my sweet 7 year old is too. This one isn’t scary, I mean the werewolf and whomping willow could be seen that way but nothing in comparison to other films. Honestly though I remember watching this film and falling for buckbeak, praying he would be okay. I laughed when Harry was trying to figure out the monster book and I felt for Harry, Sirius, Lupin and Ron when Scabbers turned out to be Peter Pettigrew, the traitor.