Harry wakes, breathing hard, and feels his lightning bolt-shaped scar, which hurts. He examines it in the mirror, but it looks normal. Harry tries to recall his dream but can only really remember hearing that Voldemort and Wormtail are planning on killing him. He walks to the window and sees nothing amiss on Privet Drive, but thinks that the last time his scar hurt, Voldemort was close to him. He knows he can't tell his aunt and uncle, Vernon and Petunia, about this: they hate magic and are horrible to Harry. They only care for Harry because Voldemort killed Harry's parents when he was about a year old. When Voldemort tried to kill Harry, however, the curse rebounded and Voldemort disappeared.
By introducing Vernon and Petunia, the novel shows what people can become when they never develop a sense of empathy. The narrator goes on to explain that Petunia refuses to believe that her son is a bully and both she and Vernon bully Harry mercilessly, as they believe themselves to be superior and Harry undeserving of attention or care. Though the novel situates them in a different category than Harry because they're Muggles, this does offer him one possible outcome for his life, should he choose to behave selfishly.
Harry has another two weeks before he returns to Hogwarts for his fourth year of school. He looks at his birthday cards and thinks of what his friends, Ron and Hermione, would say. Hermione would tell Harry to ask Dumbledore, the headmaster of Hogwarts, while Ron would nervously agree to ask his dad, Mr. Weasley. However, Harry doesn't want the Weasley family to worry, especially since he hopes that they'll invite him soon to visit them so they can attend the Quidditch World Cup. Finally, Harry realizes whom he should ask: Sirius, his godfather who, until a few months ago, was locked away in the wizard prison Azkaban for a crime he didn't commit.
By imagining what Hermione and Ron would say about Harry's dream, it shows that he already knows how to look at his experiences through different lenses to get multiple views on something. This represents the beginning of critical thinking, as it means that Harry already understands that what he experiences and knows (or thinks he knows) doesn't represent one undeniable truth; there are clearly multiple ways to interpret and react.
Because Harry was unable to clear Sirius of his crime, he couldn’t live with him this summer. However, Sirius's reputation as a murderer means that the Dursleys now allow Harry to keep his magical items with him for fear of retaliation, as they don't know Sirius is innocent. Harry spends an hour drafting a note to Sirius.
Here, Harry uses his own version of censorship in regards to what Vernon and Petunia know about Sirius. This also shows that Harry understands how to use his words and carefully share information in order to achieve a goal.