Harry leaves the Dursleys and is not sure what to do next. He is certain that he will be expelled from Hogwarts for having practiced magic outside of school, and so he considers flying on his brookstick to London, where he could live as a wizard outcast. He feels himself being watched and he is alarmed to see a large outline of a dark creature staring at him. He falls into the gutter, and is suddenly rescued by the Knight Bus, a hitchhiking service for wizards in need. Harry boards the bus after some questioning from the nosey teenage conductor, Stan Shunpike, during which Harry gives a false name, Neville Longbottom, and flattens his hair over his famous scar. The bus flies through the city, managing not to hit anything, because obstacles jump out of its way. During the ride, Harry overhears a conversation between Stan and the driver, Ernie Prang, discussing the escape of Sirius Black, and Harry learns that Black was a follower of Voldemort. Black spent twelve years in Azkaban, the wizard prison, after murdering thirteen people with a single curse.
When the Knight Bus arrives at Diagon Alley, a wizard community in London, Harry gathers his things and gets off the bus, only to be greeted by Cornelius Fudge, the Minister of Magic. Fudge reveals Harry's identity to the eavesdropping Stan and Ernie, and then he takes Harry inside for dinner, expressing great relief that Harry is unharmed. Harry thinks this concern is a bit peculiar, and he thinks it even more peculiar that Fudge has no intention of punishing him for having inflated his aunt, who, since her inflation, has been returned to her normal size. Harry does not think too much about this, however, and he falls asleep, exhausted, in the room at the Leaky Cauldron where Fudge arranged that he would stay until school begins.
Harry spends the next weeks happily wandering through Diagon Alley. He finishes his homework, eats ice cream sundaes in sidewalk cafes, admires a Firebolt broomstick in the window of a Quidditch supplies store, and buys his books for school. During his visit to the bookstore, he is alarmed to catch sight of a large black dog on the cover of a book about death omens; the dog reminds him of the dark shape he saw when leaving the Dursleys. Around this time, Harry reunites with Ron and Hermione, and while discussing their summers and coming classes, they stop by a pet store. While Ron buys rat tonic for his old and rather sickly-looking rat, Scabbers, a ginger cat leaps upon them and dashes after Scabbers. Ron is furious when Hermione emerges from the pet store having purchased the cat, Crookshanks.
The three friends join the Weasleys, where each of Ron's siblings is in his or her element. The twins, Fred and George, are busy making everybody laugh. Percy is looking stiffly annoyed, and Ginny, the youngest Weasley and the only daughter, is looking on shyly and giggling. They eat together, and after dinner Harry passes by the bedroom where Mr. and Mrs. Weasley are in a heated argument about whether or not to tell Harry that Sirius Black escaped Azbaban with the supposed intention of finding and killing Harry. Harry is not terribly frightened; he feels that Hogwarts is extremely safe, and besides, he has encountered Voldemort twice before.
These chapters establish a contrast between the magical and non-magical worlds. We see the wizard world through Harry's eyes, beginning with the eerie experience of being in the space between the worlds, outside the Dursleys' house, but miles away from Hogwarts or Diagon Alley. This discomfort is magnified when Harry spies a huge black dog watching him. In this scene, Harry's wand shoots up sparks and he is almost run over by The Knight Bus, an unusual vehicle that carries wizards out of unlucky situations and to whichever destination they desire. The bus sails through the night, and we, like Harry, marvel that all objects (houses and street-signs) jump out of its way-one more facet of the wizard world's ability to exist completely without interfering with Muggle life. The conversation between Ernie and Stan during the bus ride establishes Harry's fame among wizards, due to his defeat of Voldemort before he was old enough to remember. This fame marks Harry's experiences as a wizard in bittersweet ways; he is often given special treatment, but also special protection when he doesn't necessarily want it. He has certain inborn strengths, but he also is susceptible to certain things, like the dementors, that affect him more than others.
Once Harry is left at Diagon Alley, the wizard experience commences, as its inherent state of freedom and inclusiveness sweeps over Harry. He is able to do his homework outside in the sunshine while he eats ice cream sundaes. He is able to roam the streets of Diagon Alley, spending the money his parents left him. He independently purchases school supplies and interacts with other wizards. Harry is again in his element. One of the most significant things about this world is that although magical things appear everywhere, basic human relations are unremarkable. Wizards are entirely human in their interactions and motivations. Like any other group of friends that has been separated, Harry, Ron, and Hermione are excited at seeing each other again. Soon after, we see that tension rises as soon as Ron's old rat and Hermione's new cat appear to share mutual animosity. In this world, we see the grand, comfortable chaos of a large family like the Weasleys, filled with sibling rivalry, great parental love, and a very basic sense of mischief generated by the twins, Fred and George, and directed toward Percy, the responsible eldest child at home. We note the subtle differences between the twins, who have a few basic differences: Fred is a bit more over-the-top in his humor, beginning jokes and carrying them to their extremes, and George is somewhat subtler, more sardonic in his comments.