Camera zoom through an eerie dark scene. Gradually, the Dursley house on Privet Close comes into view, with occasional flashes of light suddenly glowing in the window of Harry's bedroom. There is Harry (Daniel Radcliffe), under his blanket with his wand, practicing his Lumos Maxima spell. Every so often, he hears something, and lies down as though asleep with his glasses on. Uncle Vernon (Richard Griffiths) would then poke in, trying to catch his nephew out doing magic. Eventually, Harry succeeds in making an incredibly intense light glow; seconds later, he's feigning sleep as Uncle Vernon bursts into the room once more.
The next day, in a flood of rain, Aunt Marge (Pam Ferris) arrives for a visit. She has her favorite bull terrier with her, fusses over Dudley, and insults Harry. Harry tries to get his uncle to sign a permission slip for something at Hogwarts, but Uncle Vernon replies that he'll sign it later, "if you behave". Harry mutters that he'll behave if Aunt Marge does. But later, while Harry removes the dinner plates and Uncle Vernon mentions how Harry attends St Brutus's school for difficult children. Aunt Marge starts going on about his "drunken" father, and as for his mother, "if something is wrong with the bitch, something will be wrong with the pup." Harry gets really upset, shouting at Aunt Marge, and when she raises her finger to begin counting Harry's shortcomings, everyone else at the table can see that the end of her finger has suddenly swollen. Her clothes burst at the seams, buttons off her blouse pelt Dudley into a retreat beneath the table, the bull terrier sinks its teeth into Uncle Vernon's leg, and gradually, Aunt Marge expands like a hot air balloon, floating into the conservatory and out of the garden.Uncle Vernon catches her hands for a moment, while the terrier bites Vernon's ankle once more, and he lets go.
Harry, thinking he's literally blown things, runs upstairs for his trunk and books. As he plunges downstairs, Uncle Vernon tries to bully Harry into reversing the spell, but Harry pulls his wand on his uncle and leaves Privet Close, with the silhouette of Aunt Marge floating in the distant sunset. But anger only takes a boy wizard so far, and by the time he reaches a small play park (some swings and other outdoor play equipment), he sits down and starts to wonder what to do. He hears something above the wind and the swings, and raises his illuminated wand to see the shape of a large black dog in a clump of bushes ahead of him, when suddenly a three decker purple bus, with the words "Knight Bus" slams to a stop next to him. "Transport for the stranded witch or wizard," says the conductor, who sells Harry a ticket. On the bus, rows of beds roll beneath a swaying glass chandelier, while a shrunken head chatters to the driver. Harry is slammed against a window at one point when the bus stops suddenly to avoid hitting an elderly Muggle slowly crossing the road, and then the crazy careering bus takes off again, zooming between two red double decker buses. Harry notices the paper the conductor is reading, with a picture of Sirius Black (Gary Oldman) on it, and learns that this man is a murderer who has served twelve years in Azkaban, the wizard's jail. Black is the only person ever to escape Azkaban, and it's believed he was the most faithful servant of You-Know-Who.
Harry is let off the bus at the Leaky Cauldron, where he went with Hagrid a couple of years before with Hagrid when he first learned about Hogwarts, and is escorted up to room 11. There, Cornelius Fudge (Robert Hardy), who is head of the Ministry of Magic, is waiting for our hero. Fudge explains how things have been corrected at Privet Close, the inflation reversed and memories altered as necessary, and chides Harry for being so foolhardy as to be out on his own when Sirius Black is on the loose. Harry wonders why Black would have any interest in him, and Fudge fudges, telling Harry he'll be off to Hogwarts tomorrow and should go to his room, He has also provided all of Harry's textbooks for the upcoming year, and Hedwig had turned up on her own five minutes before the Knight Bus deposited Harry at the inn.
When he wakes in his room at the Leaky Cauldron, Harry takes a look at the books, which include one titled, "The Monster Book of Monsters". He takes the strap off it, and then spends five minutes trying to keep the book from eating him (finally tricking it out from under the bed and landing on it with both feet). When he comes downstairs, he sees a cat chasing a rat, and then finds Ron (Rupert Grint) and Hermione (Emma Watson) arguing. Turns out the cat is Hermione's new pet, and both pet owners are taking the side of their animal. Ron also shows Harry a picture of himself with his family in "The Daily Prophet", from their summer trip to Egypt. Fred and George (James and Oliver Phelps, respectively) tease him about showing everybody that picture, and amid all the Weasley banter, Arthur Weasley (Mark Williams) takes Harry to one side for a private conversation. He feels that Harry should know that Sirius Black would probably be out to kill Harry. The wizarding world all believe that, thirteen years ago, Black killed several people while attempting to prevent Peter Pettigrew from warning Harry's parents that You-Know-Who was after them. Black might want to kill Harry, both as revenge but also to try to help You-Know-Who return to power. Mr. Weasley wants Harry to promise that, "no matter what", he won't go looking for Black. Harry agrees, puzzled as to why anyone might imagine he'd look for someone who wanted to kill him.
The trip on the Hogwarts Express is dark and rain-soaked; Hermione, Ron and Harry can only find one relatively empty compartment to sit in. True, there is a grown-up (David Thewlis) asleep against the window, but being asleep, he's hardly going to listen in on them. Hermione figures out that this is the new professor for the school, reading Prof. R. Lupin off his suitcase on the rack above his head. The train suddenly comes to a stop on a bridge above a river, and the lights on the train start to flicker out. Then the glass starts to freeze up, and a tall shape like old images of the Grim Reaper appears. Skeletal fingers with nails like talons pull the door to their compartment open, and the teenagers all shudder as the figure turns what must be its head towards each of them. But once it looks at Harry, it looks as though the creature is inhaling something from Harry. His face becomes both blurred and strained, as if he's fighting to hold on to something that's being pulled out of him. He hears some other sounds before losing consciousness. When he comes to, the professor offers him some chocolate before stating that he needs to speak to the driver of the train. Harry asks the others about what happened to them, and Ron says he felt "like I'd never be cheerful again". Harry explains that before he fainted, he heard a woman screaming, but Hermione and Ron agree that that didn't happen.
When the students enter the hall, a choir is singing with their toad chorus, "Something wicked this way comes!" and so on, followed by Dumbledore's (Michael Gambon) first greetings to the group. He introduces Lupin as the new Defence Against the Dark Arts teacher (which Snape --Alan Rickman--reacts very coolly to) and Hagrid (Robbie Coltrane) as the new professor for Care of Magical Creatures. The Gryffindor table greets the second announcement with wild applause, as Hagrid is reminded to stand by a nudge and he pushes the table back while getting to his feet. Dumbledore also explains that the Dementors (those creatures on the train) will be surrounding the castle on the hunt for Sirius Black, but they do not differentiate between their lawful prey and innocent wanderers, so all students should be careful and not go out after dark. Draco (Tom Felton) had previously teased Harry about fainting on the train because of the Dementors, but everybody seems to take the threat seriously. The Gryffindor boys then troop to their rooms, bemoaning the attempted singing of the Fat Lady (Dawn French), their guardian portrait to their rooms' entrance, and they spend their first night back at Hogwarts eating enchanted candies that cause them to make animal noises while, far in the distance outside the castle walls and lake, several Dementors float menacingly.
Gryffindors and Slytherins meet the Divination teacher, Prof. Trelawney (Emma Thompson), who seems very strange and comical at first. Ron jumps on seeing Hermione in class, asking, "Where did you come from?" Hermione dismisses him, saying, "Don't be silly, I've been here all the time." Meanwhile, Trelawney is having the class read tea leaves in each other's cups. After Ron reads Harry's leaves, thinking that Harry will suffer but be happy about it, Trelawney looks in the cup and gasps. She announces that the Grim is in Harry's leaves, and a student reads out that this is a portent of death. Hermione dismisses this after they leave, suggesting that her Ancient Runes class is much more useful. Ron wonders how she can be taking so many classes, especially as Ancient Runes and Divination are held at the same time, but she replies, "how could anyone be in two places at once."
They lope down to Care of Magical Creatures, and all are nervous on seeing the first creature Hagrid has secured for their study-- a Hippogriff, part eagle, part horse. Hagrid asks for someone to volunteer to greet the creature, and the whole class steps backwards, except for Harry. "Well done, Harry," Hagrid congratulates him, and when he turns back to the Hippogriff, Ron pushes Harry forward on the shoulder. Harry swallows heavily, and tries to follow Hagrid's instructions. For a while, it looks as though the Hippogriff won't respond to Harry's bow, and Harry slightly trips on his robes as he treads back, but Buckbeak finally bows back to Harry. During the approach, Hermione reaches down for Ron's hand, who looks down at it, then at her, before they both pull away from each other. Assured by Harry's apparent success, Hagrid beams, "Go and pat him now," and Harry, looking as if he's being punished, reaches gingerly up to stroke the beak of the animal. When Buckbeak seems happy, Hagrid decides he'd give Harry a flight, and lifts the teenager up by the waist onto the back of the creature, right near the join of horse and eagle. A beautiful scene follows where Buckbeak zooms around the castle and over the lake, even dragging its front legs by the talons in the water briefly. The entire class is whooping with pride as Harry comes back for a landing, when Draco rushes up and claims it's obviously nothing much, and the Hippogriff is a dumb, ugly brute. Buckbeak rears on its hooves, and lashes one talon out. Draco, raising his arms to shield his face, falls to the ground moaning, while Hagrid calms Buckbeak down. Hermione tells Hagrid that Malfoy has to be taken to the hospital wing, so the new professor heaves the bully up, while Draco appears to faint.
In the hall, Draco is impressing at least one girl with exaggerated stories of how the Hippogriff attacked him, and Hagrid's ineptitude as a teacher, while some of the students reading the newspaper see a report that Sirius Black had been spotted in Dufftown, which is "near" Hogwarts. The Dementors, floating eerily around the lake, are freezing the ground in their wake, killing foxgloves and other flowers.
In the Defence Against the Dark Arts class, Lupin is instructing the students on how to defend themselves against a Boggart. Hermione (who to Ron's point of view has suddenly appeared out of nowhere) explains that a Boggart can make itself appear like a person's greatest fear. Lupin then instructs Neville (Matthew Lewis) on how to fight his own personal demon, which is Snape. When Snape strides out of the wardrobe, Neville casts his Riddikulus charm, and suddenly Snape is wearing a hat with a vulture and a green dress, with a large red bag in one hand, too. Ron has the next turn, and his charm turns an enormous spider into one with skates on the end of each leg. Parvati Patel is next, and the eight foot cobra swaying before her suddenly changes into a weird clown in a Jack-in-the-Box. Harry, laughing, strides up for his turn, but even as the Boggart starts to change into a Dementor, Lupin steps in front of the boy. The Dementor shimmers into a silvery orb emerging from a group of clouds or mist, and when Lupin says, "Riddikulus," it pops like a deflated balloon. Lupin dismisses the class, leaving Harry unsure if his teacher felt he couldn't face the Boggart on his own.
When his friends all head off to Hogsmeade (which is what the permissions slip at the start of the film was all about), and Harry tries to accept being left behind, he finds Lupin and asks why Lupin intervened. Lupin explains that he thought the class would be too frightened by Lord You-Know-Who appearing. Harry replies that he first thought of Voldemort, then remembered the Dementors. "I'm impressed," Lupin concedes, saying how this shows that the thing Harry is most afraid of is fear itself. He also explains that he recognized Harry the moment he saw him, because Harry has his "mother's eyes". Lupin knew both of Harry's parents when he was younger, and continues that James Potter had a talent for trouble, "a talent, rumor has it, that passed on to you." He predicts that Harry will come to see that he is more like his father than he, Harry, as yet can appreciate.
The Gryffindors are unable to enter their rooms one day soon after; Percy, declaring that he is Head Boy and can deal with things, pushes his way through and finds that the Fat Lady's portrait has been slashed and she herself is missing. Dumbledore arrives with Filch, and Filch sees where she has hidden herself. After Dumbledore beseeches her, the Fat Lady reveals that Sirius Black tried to enter the Gryffindor rooms, and attacked her when she refused. But she cannot serve as guardian to the rooms in her present state, so the Gryffindors must spend the night in sleeping bags in the hall. Dumbledore and Snape walk among the sleeping students, with Snape suggesting that someone inside Hogwarts must have let Black in, but Dumbledore insists that his staff are all trustworthy, and that Harry doesn't need to know the full extent of Black's crimes. The Dementors draw closer in to the castle, moving onto the actual grounds.
One day, then, Snape strides into the Defence Against the Dark Arts class, demanding that the group turn to page 394 in their books. While Harry wonders where Lupin is, Ron is again surprised to see Hermione suddenly in her chair. Snape wants someone in the class to state the difference between an animagus and a werewolf; Hermione answers despite Snape ignoring her. Snape dismisses Hermione as a smug know-it-all, and while Ron kind of agrees with this, it grates to agree with Snape. Snape, meanwhile, demands that everyone in the class write a two parchment essay on how to recognize a werewolf. Harry points out that he has a Quidditch game the next day; Snape says that injury will not be an accepted excuse for not completing the essay.
At the game, the rain again is pouring down. The teams are all wearing goggles, including Harry, as he darts through the sky looking for the Golden Snitch. He suddenly sees a cloud swirl to form the dog-like shape of the Grim, then catches a glimpse of the Snitch. But as he flies after it, Dementors appear all around him. Despite trying to fly away from them, eventually Harry is so weakened that he loses his grip on his broom, and begins a hundred-foot descent towards the ground. A few seconds before darkness overwhelms him, he hears Dumbledore shout, "Arresto momentum!", but he knows no more until he wakes up in the hospital wing. Hermione tells him how furious the headmaster was at the Dementors being on the Quidditch grounds, then falteringly says nobody blames him for losing the game. Then, worse, Ron reveals that after Harry fell off his broom, it flew within reach of the Whomping Willow, and is now kindling and twigs.
Lupin commiserates with Harry over the destroyed broom, which can't be repaired magically or otherwise. He also explains that the Dementors affect Harry more deeply because Harry has experienced the kind of pain and tragedy which most of the students will never know, if they're lucky. He also promises to try to help Harry find a way to fight the Dementors after the holidays.
Harry, fed up with being unable to visit the wizarding town of Hogsmeade, tries to sneak out of the castle in his invisisbility cloak, but Fred and George are waiting and, somehow, catch him even though he's invisible. The twins then explain that, reluctantly, they are going to give Harry the Marauder's Map. When a person says, "I solemnly vow that I am up to no good," the map reveals all the passages, secret or otherwise, in Hogwarts, as well as the location of every person in the castle at that time. They recommend one tunnel for Harry, as it leads to Honeydukes sweets shop, and tell him that when he has finished, he should say, "Mischief managed" in order for the parchment to once again appear as a blank piece of paper.
Harry uses the map, emerging in the candy store, then goes out (in his cloak) to look for his friends. Ron and Hermione are looking at the Shrieking Shack, when Draco and his lackies come to tease and bully. Harry takes advantage of his invisibility to pelt the baddies with snowballs and pulls Goyle's (Josh Herdman) trousers down. The threesome end up back in Hogsmeade when Harry spots Cornelius Fudge arriving outside a tavern, muttering indistinct warnings about Sirius Black. Harry, under his cloak and invisible, follows Fudge in, but Hermione and Ron can't follow. So Harry is alone when he hears Prof. McGonagall explaining that the worst part of Black's treachery, beyond his killing Peter Pettigrew and a crowd of innocent bystanders, is that he is Harry's godfather and the trusted friend of James and Lily Potter. Harry rushes out of the tavern, followed by his friends (who can find his path by the people he's knocked over in his hurry). Harry is sobbing in a forest clearing when Hermione finally pulls the cloak off him, and Harry shouts that he hopes Black does find him so that he can kill Black.
Lupin begins trying to teach Harry a Patronus charm, which is very advanced magic. Harry must find a happy memory, and the strength of the memory will determine the strength of the Patronus. The Patronus will act as a shield for Harry, providing something the Dementor will try to feed off while protecting the wizard. Harry fails on his first try, but Lupin explains he would've been shocked if Harry had succeeded on the first go (with a Boggart for the practice attempt). Harry tries again, using a different memory (possibly one of the times he saw his parents in the Mirror of Erised from the first film), and manages to hold off the Boggart-Dementor.
Scabbers, Ron's rat, has vanished, and Ron decides that Hermione's cat must've eaten him. She replies that Ron should take better care of his pet, but the kids stop fighting when they see Hagrid, who's come back from the committee meeting about Buckbeak. Draco and his father, Lucius Malfoy, have both presented a case loaded with lies about the violence of the Hippogriff and Hagrid's unsuitedness to being teacher, exaggerating how badly Draco has been hurt and downplaying how he baited the creature, despite Hagrid's warning and attempted intervention. Dumbledore spoke up for Hagrid and the creature, and while Hagrid isn't being punished, Buckbeak is to be executed.
One night, after Ron briefly wakes from a bad dream where a group of spiders were forcing him to tap dance with them, Harry is looking at the Marauder's Map, when he sees the name "Peter Pettigrew" walking along the halls of Hogwarts.Harry decides to look for this person (after all, Pettigrew is supposed to be dead, with only his finger left behind of his corpse), but at the instant he is supposed to be right on top of Pettigrew, he sees himself in a mirror and is spooked. A scurrying sound passes him, but no person. Then Professor Snape appears in the hall, and he demands that Harry turn out his pockets. On seeing the Marauder's Map, Snape taps it with his wand, commanding it to reveal its secrets. The parchment replies that Messieurs Moony, Padfoot, Wormtail and Prongs present their compliments to Professor Snape and wish him to keep his abnormally long nose out of other people's business. Lupin comes at this moment, and declares that the parchment is obviously meant to insult anyone who asks it to reveal its secrets, then he takes it since Snape has already said it would be more his (Lupin's) field of expertise. Lupin demands Harry to follow, then chastises Harry for taking such risks. He knows that James also never gave much though for rules, but James and Lily gave their lives for their son. Before leaving Lupin, Harry says he thinks the map must lie sometimes, as it said that Peter Pettigrew was walking the halls of Hogwarts. Lupin looks puzzled, as everyone knows Pettigrew is dead.
Hermione finally gets her full of insults from Prof. Trelawney, pushing the crystal ball she and the boys had been supposed to find the future in down the hall and stairs. Harry, on leaving the class, picks up the ball and tries to return it to the classroom, As he sets it on its base, for a moment, he sees the face of Sirius Black, calling his name. He then feels Trelawney's hand on his shoulder, and is really spooked when Trelawney begins to speak in a ghostly double voice. She predicts that tonight, the Dark Lord's servant will return to his master, and that that servant will eventually bring You-Know-Who back to power. Then she shakes herself, and appears to not be aware of having said anything strange or special. Harry practically leaps down the circular staircase to get away.
Meanwhile, ravens are gathering all around the castle while a hooded man sharpens an evil-looking axe. Hermione leads Harry and Ron towards Hagrid's, intent on being with the gameskeeper while Buckbeak is executed. On the way, the trio see Draco congratulating himself on the execution, and Hermione draws her wand level with Malfoy's snivelling adam's apple. The boys cry out that Malfoy isn't worth it, and Hermione pulls her wand back, only to let fly with a beautiful punch to Draco's nose. "That felt good," she declares. "Good?" Ron squeaks. "It was bloody brilliant."
Hagrid tells the teens that Dumbledore is planning to come down to be with him, and then says they ought to go before the officials arrive, as "especially Harry" shouldn't be out after dark, which will occur in a few minutes. But they get distracted when Hagrid suddenly pulls Scabbers out of a pot on a shelve. Hermione says Ron owes someone an apology, and Ron says he'll give one to the cat once he sees the feline, The three heroes don't leave the place for awhile, though, until rocks start pelting through a window and direct their attention to Dumbledore, Fudge, and the executioner walking up to Hagrid's hut. They head out the back door, hiding briefly behind some large pumpkins, although Hermione thinks she hears something and turns around for a moment. The kids then rush up the hill, and although they can't see everything because of the piles of pumpkins, they see the executioner lower his axe where Buckbeak had been chained up. Hermione leans against Ron for support, crying, while Harry leans in on her other side to hug her, too.
But Scabbers breaks this sorrow by biting Ron's thumb. Ron drops the rat, which races across the darkening grounds. He follows his pet, with Harry and Hermione close behind. By the time he catches Scabbers, Harry realizes that they are near the Whomping Willow, but before they can get away, a big black dog strides out of nowhere. The teenagers all freeze for a moment, and then the dog leaps forward at Ron, catching him by one leg and pulling him beneath a clump of tree roots where there's a hole between roots and ground. Harry and Hermione have to fight the Whomping Willow, and in the end the Willow tosses them down the same hole.
They discover they're in the Shrieking Shack, reputed to be the most haunted building in Britain. Harry and Hermione find Ron, whose leg is badly hurt, on an upper floor, when out from the shadows emerges a dog. The dog then becomes Sirius Black-- Black is an animagus, a wizard who can voluntarily assume the form of an animal. Hermione stands in front of Harry, saying if Black wants to kill Harry, he'll have to kill all three of them. Black laughs that only one will die that night, and Harry snaps that it will be Black. The boy throws himself on the older wizard, but before he can use his wand to try to kill Sirius, Prof. Lupin enters the shack. The two adults seem wary of each other at first, then hug. Hermione is stunned; she kept Lupin's secret all this time, thinking he was Harry's friend. She tells the boys that the professor of the Dark Arts is, in fact, a werewolf (she figured it out when Snape made them do the essay). Black and Lupin continue to talk about killing "him", but at some point, one of them mentions Peter Pettigrew.
Harry is perplexed; Pettigrew is dead, and the Map lied when it said it saw him in Hogwarts. Black states that the map can't lie, and starts to try to explain. But just then, Snape comes in and disarms Lupin. He thinks this is proof that Lupin has been helping Black all along, and wants to hand Sirius over to the Dementors for their worst punishment, the Kiss (which steals the soul of the person Kissed). Harry edges over to Hermione, pulls her wand from her jean's pocket and sends Snape crashing against a wall. He then demands that Black and Lupin explain what they mean about Pettigrew.
Eventually, it comes to this: Pettigrew betrayed the Potters to You-Know-Who, and when Black cornered him, cut off his finger before casting the curse which killed all the innocent bystanders and changing into a rat. No-one would believe that Pettigrew, who vanished and who had always been known to be the weaker wizard, could've been responsible for this kind of death and destruction. Pettigrew made his way to the Weasley family and hid there as a rat ever since. Black turned Scabbers back into a human (Timothy Spall), at which point Ron finally starts to accept the story. Pettigrew snivels that the Dark Lord had awful powers; "What would you have done?" he asks Sirius. "I would've died rather than betray my friends," the former prisoner snarls. Black and Lupin are now ready to kill Pettigrew, but Harry intercedes. He doesn't want his father's two best friends to be guilty of murder; better to turn Pettigrew over to the Dementors.
After climbing out from beneath the Whomping Willow, Hermione and Ron encourage Harry to talk to Sirius on his own. Sirius, awkwardly, offers to give Harry a home, although he feels sure that Harry probably prefers being with his aunt and uncle. Before Harry can correct this misunderstanding, a full moon appears over the horizon. Lupin, it seems, hasn't taken a potion which would have helped somehow with his condition, so while Sirius pleads for Lupin to hold onto his mind, the wolf takes over. The wolf throws Sirius down a hill, and suddenly Prof. Snape emerges to protect the teen heroes.
He is also attacked, and the wolf then moves towards Harry menacingly, until another wolf cry in the distance lures him away. Pettigrew changes back into a rat and escapes in the confusion (without Snape seeing him). Harry runs looking for Sirius, eventually finding him at the edge of the lake with a flock of Dementors circling in for the feast. They pull on both Sirius and Harry, both of their faces blurring as if warped in the direction of whichever Dementor is ingesting at the time, and Harry tries to summon a Patronus. He succeeds in raising a shield, but there are far too many Dementors for that shield to hold. Then, about fifty yards away, a full Patronus appears, like a glowing white stag. The Dementors flee, almost dissolving in on themselves, and Harry briefly sees someone behind the Patronus before he loses consciousness.
He comes to in the hospital wing. Dumbledore explains that Black is soon to be given the Dementor's Kiss, and tells the threesome where he's being locked up. He then says something about how a child's voice, "however honest and true", doesn't matter when no-one will listen, as he slaps his hand against Ron's broken leg (held in traction with a large cast on it). Ron whimpers, and Dumbledore continues that they need more time, and that if things go well, more than one innocent life could be saved that night. He then tells Hermione that three turns should do it, winks, and leaves the hospital wing.
Hermione pulls a long chain out from beneath her shirt, with a charm on it. She loops the chain around both her and Harry's necks, twists the charm inside a circle three times, and suddenly time goes backwards around her and Harry. The charm is a Time Turner; Prof. McGonagall gave it to her at the start of the school year so she could make all her classes and be in two places at the same time. She then leads Harry down to Hagrid's hut, pausing to admire how she punched Malfoy. It seems that when the rocks came through the window in Hagrid's hut to make the kids see Dumbledore and the others coming down, it was Hermione that threw them. Harry then manages to release the chain holding Buckbeak in place for his execution, but the hippogriff refuses to move until Hermione lures him away with dead ferrets. Apparently when the executioner swung his axe down, he sliced open a huge pumpkin out of frustration at being denied the proper execution.
The teenagers and Buckbeak then head towards the Whomping Willow, seeing first Lupin, then Snape enter. They have to wait until the others emerge, and in fact, Hermione makes the wolf call that tempts the werewolf away from Harry. Unfortunately, it causes him to follow her and the time-turned Harry. Buckbeak fights the werewolf away from Hermione and Harry, beating down Lupin-wolf with its talons. "Prof. Lupin's had a really tough night," Harry sighs, but then he waits. He believes the Patronus was somehow conjured by his father, and is sure that James Potter will somehow appear to save Sirius and his self that are being attacked by the flock of Dementors. But finally, he realizes that it was his time-turned self who conjured the Patronus, and manages this feat of majorly advanced magic because, "I'd already seen myself do it, so I knew that I could." Hermione sees this as sketchy reasoning, but the results are successful.
The two ride Buckbeak to where Sirius is being held, and break him out.Harry is sad because he really wanted to live with Black; plus, nobody else will know that he's innocent. "But you know it, and that'll do for now," Black replies. He then tells Harry that if the boy wants his godfather, just look in here-- and places his hand over Harry's heart. He then mounts Buckbeak and flies to freedom. Harry and Hermione race to get back to the hospital wing in time (Dumbledore warned them to be back before the last chime of when they first spoke), and Ron does a double-take when his friends seem to vanish from one spot only to appear in another five feet away from the first.
Lupin, meanwhile, has resigned, as someone has let it slip that the teacher of the Dark Arts is a werewolf. He knows that if he tried to stay, the owls would come from every direction of outraged parents fearing for their children's safety. Harry moans that none of what they did made any difference; Lupin disagrees. The truth was uncovered and an innocent man escaped a terrible fate. He then returns the Marauder's Map to Harry, seeing as he is no longer his professor, but feels sure he'll meet Harry again some day.
Harry, saddened, mopes his way back to the hall, only to find several Gryffindors clustered around the table. Many of them call out, "What luck", "Can I have a turn after you do, Harry?" and so on. Neville claims that Fred and George provoked him to open the package, which the Weasley twins deny, and then Harry sees that on the table is the newest and hottest broom available to wizards, a Firebolt. He takes it to the courtyard and mounts it quickly, screeching across the sky above Hogwarts, his face blurred... this time with joy.
The closing credits are done over a Marauder's Map, with many things happening along the edges, like people rushing out of a Stink Shop when something pops, bird footprints in the Owlery, a pair of shoe prints becoming bare feet before turning into dog pawprints, and so on. You may not feel it's worth the wait, but it's interesting all the same.