Chapter 14 - "The Unforgivable Curses" - In which the fourth-year students learn about the Unforgivable Curses in their first lesson with Moody, Moody takes Neville to his office, Harry and Ron fake their Divination homework, Hermione starts SPEW, and Harry receives a letter from Sirius saying he's returning to Britain.

Classes Begin
At lunch Hermione shovels down her food and rushes to the [library], despite not yet having been assigned any homework, which Harry and Ron can't figure out.
Harry and Ron follow lunch by heading to the [North Tower] and [Divination] class. Not surprisingly, Trelawney punctuates the new school year by once again predicting dire things for Harry. She also assigns loads of homework, which Harry suspects might be because she overheard Ron joking about Uranus.
The Ferret
Harry, Ron, and Hermione meet up after class and run into Malfoy, brandishing a story about Mr. Weasley. When Harry retorts, though, Draco tries to jinx him - and is stopped when Moody himself appears and turns him into a ferret. Finally, McGonagall arrives and reverses the spell, but not before the scene is etched forever into the students' memories.
Ron spends dinner basking in the memory of Malfoy the ferret, and Hermione once again shovels her food down and bolts for the [library]. When Fred, George, and Lee Jordan arrive, they describe their first class with Moody to the fourth years, unable to believe how cool their lesson was.
Over the next two days, Snape seems to be in a fouler mood than ever, Hermione continues spending all her free time in the [library], and the [Gryffindors] are anxious for their first lesson with Moody.
Neville Is Upset by the Cruciatus Curse
Moody's first class with the fourth years is a radical departure from their other lessons, as he demonstrates the [Unforgivable Curses] on spiders. Harry, however, isn't particularly excited by the lesson, and neither is Neville, who is clearly upset by the demonstration of the [Cruciatus Curse].
After [Defence Against the Dark Arts], Hermione rushes to comfort Neville, who is obviously extremely bothered by the demonstration of the [Unforgivable Curses]. Moody guides him away, and as Hermione also rushes to the [library], Harry and Ron continue discussing the lesson.
Harry and Ron run up to their [dormitory] to fetch their [Divination] homework, but find Neville, still obviously bothered but reading a book on [Herbology] that Moody loaned him.
After a feeble attempt at their [Divination] homework, Harry and Ron resort to making up everything for their star charts. As they continue, Harry notices Fred and George plotting over a sheet of parchment, and wonders what they're doing.