Ron and Hermione are so angry with each other over what looks to Ron like Crookshanks' success in eating Scabbers that Harry fears this is the end of their friendship. Harry thinks that Ron is right and Crookshanks did eat Scabbers, but Hermione loses her temper with Harry when he points this out. Fred and George fail to cheer Ron up, but Harry is able to convince him to come with him to Quidditch practice so he can ride the Firebolt. At the pitch, Madam Hooch inspects the broomstick until Oliver reminds her that they need to practice. Before they mount, Oliver says that the Ravenclaw Seeker will be Cho Chang, who's very good but rides an old broom.
Notice that the narrator never says that Harry was particularly angry with Hermione about Scabbers's death; he was able to treat what seemed to have happened as fact without getting emotional about it. This is a mark of maturity for Harry, though his inability to see how that could be a sensitive subject for Hermione indicates that he still has a long way to go.
Ron takes his turn on the broom and flies until Madam Hooch wakes up from her nap and insists they go inside. Harry and Ron are halfway to the castle when Harry notices a pair of glittering eyes in the darkness. Ron lights his wand and they see Crookshanks. Ron angrily throws a stone, but Crookshanks disappears. Harry is secretly relieved; he thought the eyes belonged to the Grim.
Harry's fear of the Grim shows that even if he finds Divination a bit ridiculous, he does take the Grim very seriously. While Crookshanks is still a disliked figure at this point, he's not scary like a death omen and is rather a sign that things are normal and safe.
The next morning, Harry takes the Firebolt to breakfast with him. The Slytherins look awestruck and even Cedric Diggory compliments Harry on the broom. After Penelope Clearwater looks at the Firebolt and heads back to her table, Percy urgently whispers to Harry that Gryffindor has to win—he and Penelope bet ten Galleons on the game, and he doesn't have the money to lose. Malfoy tries to taunt Harry about the Firebolt having a parachute, but the Gryffindors turn him away.
Again, when Cedric Diggory congratulates Harry on the broom, it shows that he believes entirely in fairness and making sure that things play out in a just way. Percy's request to Harry shows that he also has a habit of bending the truth to make himself look better to Penelope, which begins to normalize the practice.
Cho Chang is the only girl on the Ravenclaw team and as Harry approaches, he feels his stomach drop. Madam Hooch instructs the teams to mount and kick off. Lee Jordan's commentary focuses mostly on the Firebolt and its qualities, though McGonagall tries to keep him on track. Cho tails Harry and, as he dives for the Snitch, she cuts him off. Harry leads Cho around the pitch at a quick pace and finally sees the Snitch. As he races for it, Cho screams and points to three dementors on the field. Harry pulls his wand out, shouts "Expecto Patronum," and continues towards the Snitch as something leaps out of his wand. He catches the Snitch and Gryffindor wins.
The fact that something "leaps" out of Harry's wand suggests that he created a real, distinct Patronus this time. It's important to remember that this happened during a moment of great excitement for Harry, which shows that Lupin may have undersold how happy or excited a person needs to be in order to properly conjure a Patronus. In this situation, being so close to the Snitch gives Harry the strength to focus on the task at hand.
The team descends upon Harry and then the crowd engulfs them. Harry hears Lupin beside him complimenting him on his Patronus. When Harry says he didn't feel anything, Lupin explains that the dementors weren't real and leads him to where Malfoy, Crabbe, Goyle, and the Slytherin Quidditch captain are struggling to crawl out of black robes. McGonagall shouts at them as Ron laughs.
Even though these dementors weren't real, Harry still gets the valuable experience of having created a perfect Patronus under pressure. This suggests that there are times when the facts of a situation aren't as important as its outcome.
Fred and George begin a party in the Gryffindor common room. Hermione, however, doesn't join in. Though she says she came to the match, she insists that Ron doesn't want her to join the party. Ron loudly comments that Scabbers used to love party food, which sends Hermione into tears. Ron tells Harry that if Hermione would act sorry, he'd stop.
The party ends after midnight when McGonagall tells everyone to go to bed. A scream interrupts Harry's dream, so he sits up, opens his curtains, and sees Ron looking terrified. Ron says that Sirius Black was above him with a knife. Doors start to open and people tell Ron that he was just dreaming. McGonagall returns to the common room, annoyed. Ron finally shouts that Sirius Black was in the dormitory and tells McGonagall to ask Sir Cadogan if he let Black in. Suspiciously, McGonagall steps out of the portrait hole and Sir Cadogan brightly says that Black had a list of passwords. McGonagall angrily asks who wrote the list and Neville raises his hand.
When people try to discredit Ron and don't take him seriously, it shows how a large group of people is capable of not being willing to hear the truth—even when, as is the case with the Gryffindors, they all care about Ron and want him to be safe. Ron's ability to bring in Sir Cadogan to corroborate his story reinforces the importance of having witnesses and other people to confirm events, as it's the only way that people are willing to take him seriously.