In Potions the next day, Neville melts his sixth cauldron and Snape gives him detention for it. Ron and Harry know that Snape is so vindictive because of Moody, whose job he wants and whom Snape seems oddly afraid of. On Thursday, the Gryffindors have their first class with Moody. Harry, Ron, and Hermione sit right in front with quills ready, but as Moody enters the room, he tells the class to put their writing utensils away. He takes roll and then says that Professor Lupin sent him a letter detailing what they learned last year, and this year, he's going to teach them about curses.
Harry's recognition that Snape is afraid of Moody suggests that the two have history together, while the fact that Harry picks up on this at all speaks to his growing critical thinking skills. As a teacher, Moody shows that he understands that his job is to prepare students to deal with the world they live in, one in which curses abound. This demonstrates his recognition that these fourth year students are at a point in their lives where they're ready to accept these hard truths about their world.
Moody says that the Ministry of Magic wants him to only teach countercurses, but Dumbledore wants the students exposed to illegal Dark curses now. He asks the students to name illegal curses. Ron names the Imperius Curse and at this, Moody pulls a large spider out of a jar. After muttering "Imperio," he makes the spider perform cartwheels and dance. Everyone laughs until Moody growls that a victim can be made to do anything, including kill themselves. When he asks for another curse, both Hermione and Neville raise their hands. Neville offers the Cruciatus Curse and confirms that his last name is Longbottom.
By showing the students these curses, Moody makes the case that knowledge is power and the only way for the students to be properly prepared for adulthood is to have as much knowledge as possible. While none of the creatures that Lupin taught last year were evil, per se, the curses that Moody is talking about definitely are. This shows that a crucial part of coming of age is being able to handle the scarier parts of life.
Moody makes the second spider bigger before performing the curse on it. When he does, the spider twitches, rocks, and jerks in pain. Hermione shrilly yells for Moody to stop and Harry sees that Hermione's eyes are fixed on Neville, who looks more horrified than anyone else. Moody returns the spider to its normal size and then asks for the final curse. Hermione gives it: Avada Kedavra. This is the Killing Curse and Moody uses it to kill the final spider in his jar. It dies in a rush of green light and Moody explains that there's no way to block this one.
Hermione's decision to ask Moody to stop his demonstration shows, first of all, how tuned in she is to her classmates' emotional needs. Then, standing up to a teacher suggests that as Hermione learns to not take the authority of books seriously, she's also learning that she doesn't always have to take teachers seriously--they're biased and human, just like books are.
Harry realizes that this is how his parents died and loses himself in thought. He returns to the present as Moody says that his goal isn't to teach the class the curses, but to teach them what's out there in the world. He says that the three curses are known as the Unforgivable Curses and using one lands a person in Azkaban for life. The class takes notes until the period is over and as the Gryffindors spill into the hallway, most of them discuss the lesson as though they'd seen something fantastic. Harry and Hermione don't agree, and Hermione leads Ron and Harry towards Neville. Neville's voice is high and he seems strange and distant. Moody approaches the students and invites Neville to join him for tea. He leads Neville, who looks terrified, away.
The Gryffindors' interpretation of the lesson as being something fun again speaks to the success of the Wizarding world at keeping its young people from having to confront the horrifying past. For students like Neville and Harry, however, who live with the results of Voldemort's reign every day in very tangible ways, the past is already much closer to them. This suggests that in order for the other students to learn to appreciate these curses and the evil they represent, they'll need to accept that the curses can horrifically change a person's life.
After dinner, Hermione returns to the library and Ron and Harry return to Gryffindor Tower. Harry asks if Dumbledore will get in trouble for authorizing Moody to show them the curses, but Ron thinks both men will be fine. As they fetch their things for Divination, they find Neville reading a book about Mediterranean water plants that he got from Moody. He looks much calmer and says that Moody heard from Professor Sprout that Neville is excellent at Herbology. Harry and Ron begin their Divination homework, which entails making predictions about their next month. After an hour, they decide to make the predictions up. As Harry works, he notices Fred and George working in a corner. They almost look secretive and Harry overhears George say that they have to be careful not to sound accusatory.
Ron's belief that both Dumbledore and Moody will be fine despite going against Ministry guidelines shows that at this point, Ron places more trust and faith in Dumbledore than he does in the Ministry; he believes that Dumbledore is exempt. This suggests that Dumbledore doesn't have to play by the same rules as other adults in the Wizarding world, given that he clearly ignores them. However, note that Ron isn't worried because he agrees that learning about the curses was valuable--this suggests that breaking rules for the sake of good and education is a noble endeavor.
A few minutes after Fred and George leave for bed, Hermione enters the common room with a sheaf of parchment and a box. She looks at Ron's predictions, notes that he's going to drown twice, and then finally shows them the contents of her box: badges that say "S.P.E.W." She explains that it stands for the Society for the Promotion of Elfish Welfare, a group she's just started and needs Ron and Harry to join. Ron insists that house-elves are happy, but Hermione talks over him to say that their aims are to get fair wages and working conditions, as well as getting an elf into the Ministry to improve representation. She names Ron treasurer and Harry secretary.
It's important to keep in mind that, like Percy, Ron stands to benefit from the system that enslaves house-elves and therefore, has little reason to stand up for them--and as far as he's concerned, the way things are is just fine. This suggests that if Hermione is going to be truly successful in her endeavor, she has a great deal of consciousness-raising to do among wizards, as they must realize that they need to treat elves with kindness and compassion.
Before either Harry or Ron can respond, Harry notices Hedwig at the window. She has a note from Sirius saying that he's coming north to be closer to Hogwarts, given the strange rumors he's heard. He also notes that Dumbledore is "reading the signs." Harry is furious; he doesn't want Sirius to return and get caught. He angrily goes to bed.
Sirius's use of "reading the signs" begins to open up the idea of reading critically to other types of reading--in this case, Sirius is implying that a variety of things are going on that, taken together, point to trouble, and that a person can "read" this situation like a book.