Sirius Black, who people believe to be a member of Lord Voldmort’s army, escapes the Prison of Azkaban to find Harry. It is the third year of Harry’s schooling and he receives a Hogsmeade visit form that should be signed by the guardian in order to permit them the visit. He finds it difficult to ask Uncle Vernom as he is already pissed about the call from Ron Weasley, who happens to be his best friend. Meanwhile, Uncle Vernom informs Harry about the arrival of his sister, Aunt Marge. Harry totally dislikes her and the feelings are mutual from her side too. After the announcement, Harry blackmails his Uncle saying that if he does not sign the permission for than he wouldn’t keep up with the lie and tell her everything about Hogwarts. Uncle Vernom panics and agrees to sign the form only after monitoring how he behaves. But after the arrival of Aunt Marge, everything starts to go out of hand. She just couldn’t stop insulting Harry’s mom and dad, which eventually made Harry so mad that his anger discarded magic. As the outcome, Aunt Marge started to expand like air filled in a balloon. Mad and terrified Harry storms out of the house with his bag pack.
After walking few street away, he sits down and starts thinking what he should do next when his guts tells him that somebody is watching him. He uses his wandlight to search around and sees a big dog staring at him. He is about to approach him when a bus appears out of nowhere. “The Knight bus” it says that is in the service for Witch and Wizards. Harry is scared that he would be punished for using magic outside of school, so he hides his identity and introduces himself as Neville Longbottom to Stan, the driver.
Harry reunites with his two BFFs and gets away from the punishment that he should have gotten after using magic out of school. However, there was new thing in a row. Firstly, Hermione’s adopted cat, Crookshanks. Crookshanks, of course, has it in for Ron’s pathetic rat, Scabbers, which leads to a long series of arguments between Ron and Hermione.
On the way back to school, some Dementors, the scary guards of Azkaban, enter the train to searching for Sirius Black. Dementors are happiness sucker, they apparently feed on people’s good memories and leaves them with bad ones. As Harry had been through too much, he loses his consciousness as the Dementors proceed to his compartment.
At Hogwarts, changes are afoot. Remus Lupin arrives as the awesome new Defense Against the Dark Arts teacher, and Hagrid is the new Care of Magical Creatures teacher. The year progresses and Harry is busy kicking butt in Quidditch, Meanwhile, everyone is preoccupied with fear of Sirius Black, who breaks into Hogwarts twice during the school year.
Harry devotes most of his time to Quidditch, sneaking into Hogsmeade that was the courtesy of a magical map provided by Fred and George, and working with Professor Lupin on casting the Patronus spell, a defense against Dementors.
Midway through the year, the trio eventually reconcile in time to help Hagrid with his eleventh-hour appeal to save Buckbeak, his hippogriff. Hagrid loses the appeal. On the day of Buckbeak’s execution, the Harry, Ron, and Hermione find Scabbers alive and well in Hagrid’s cabin. The trio ran away right after Dumbledore comes in with the Minister and the executer. The trio hides behind and sees Buckbeak being executed. The rat in Ron’s hand starts to move madly and bites his finger and runs off. Ron finally catches him, however, right at that moment a gigantic dog leaps on to him and drags them into the creepy Shrieking Shack. Harry and Hermione follow Crookshanks, the cat and slid through the tunnel under the Whomping Willow and reach the Shack. The find Sirius Black who happens to be an Animagus. Harry strats blaming him for his parents death and they get into a fight. Sirius tries explain however Harry was in no mood. Soon Lupin and Snape show up and the shocking truth are slowly unfolded starting with Lupin being a werewolf, Scabbers the rat being Peter Pettigrew who being the friend of Harry’s Parents, sold them to Voldemort. Lupin and Sirius being Harry’s parents best friends and Black being his godfather is also laid out here.
Pettigrew escapes when Lupin starts turning into a wolf after coming out of the Shack. As the proof of Sirius’s innocence is not proven he is therefore taken into custody. That is where Dumbledore comes in and asks Hermione to use the Time-turner, a secret on how she had been attending all the heap of classes. So Harry and Hermione travel back in time to that afternoon and manage to save both Buckbeak and Sirius. Harry saves Sirius by casting a super powerful Patronus against the creepy Dementors.
The school year ends and everyone heads home for the summer. Lupin resigns deciding not to trouble Dumbledore much. Sirius after being saved goes into hiding and keeps in touch by letters. With that the trio parts ways for yet another summer.
Morals: Truth always has three sides: your, mine and the truth. Harry Potter Series is particularly about friendship and no wonder they have set quite a high example. And one more thing, the betrayer is always someone close to you.