"ATTACK! ATTACK! ANOTHER ATTACK! NO MORTAL OR GHOST IS SAFE! RUN FOR YOUR LIVES! ATTAAAACK!"
Harry, cured, goes looking for Ron and Hermione in the girls’ toilet where they are brewing the Polyjuice Potion. Hermione steals boomslang skin from Snape’s office while Harry creates a diversion in class. A duelling club is formed by Lockhart and Snape, and during the first meeting Harry learns that he is a Parselmouth when Malfoy conjures a snake. Rumours fly suggesting that Harry is responsible for the attacks on students, a rumour which is strengthened when Harry stumbles on the Petrified forms of Justin Finch-Fletchley and Nearly Headless Nick.
Calendar and Dates
The chapter begins on a Sunday in November, the morning after the Gryffindor-Slytherin match. The chapter ends in December, on the same day as what would have been the last Herbology lesson of the term, the day after the first (and only) meeting of the Duelling Club.
Interesting facts and notes
During my first reading of Order of the Phoenix, I (MLW) wondered whether Harry, Ron, and Hermione would get around the ban on organizations by reviving the Duelling Club, but disbanding all existing organizations and requiring them to reform eliminated that possibility.
This chapter provides our initial introduction to the concept of the language of Parseltongue and of the people who speak it. The reader is at a disadvantage regarding Parseltongue; Harry's status as a Parselmouth, coupled with his being the viewpoint character for nearly the entire series, means that we are not normally made aware of when Parseltongue is being spoken and when it isn't, since Harry has generally spoken it without being aware of it.
In the Muggle world, duelling has only really been out of style since about the mid-nineteenth century, although it was made illegal before that in many places. Flitwick's status as a duelling champion implies that it is treated as a formal competitive sport in the wizarding world, as well as a means of settling disputes (the latter is implicit in "The Midnight Duel" in Philosopher's Stone).
...he clumsily fed himself porridge left-handed.
As Harry passed the library, Percy Weasley strolled out of it, looking in far better spirits than last time they'd met.
Conjuring up portable, waterproof fires was a speciality of Hermione's.
Hermione used this spell several times the previous winter, often in conjunction with Snape: setting him on fire during Harry's first Quidditch match (PS11) and the fire in the courtyard incident when Snape confiscated Harry's library copy of Quidditch Through the Ages. Sure enough, on the present occasion Snape crops up again, since Hermione has worked out that she and the boys will have to steal ingredients from Snape's private stores in order to make the Polyjuice Potion.
"Wish Dobby'd told you what kind of monster's in there, though. I want to know how come nobody's noticed it sneaking around the school."
Usually Hermione provides logical analysis for the team, but on this occasion Ron has seized on the key point.
"And you, Miss Granger - you can partner Miss Bulstrode."
Behind him walked a Slytherin girl who reminded Harry of a picture he'd seen in Holidays with Hags. She was large and square and her heavy jaw jutted aggressively.
The first mention of Millicent Bulstrode by name since her Sorting, although at this point she has been sharing Harry's Potions class for a year and a half, and logically would have also been at Harry's first flying lesson. We will next see her in person in OP as a member of the Inquisitorial Squad.
We do not know if Millicent is one of Pansy's 'gang of Slytherin girls' or if she is outside their clique. Their shared status as members of the Inquisitorial Squad seems to suggest that she is a member of Pansy's circle, but there is no hard evidence on this point. Note that the mention of 'gang of Slytherin girls' in the plural suggests that at least there is at least one more Slytherin girl in Harry's year that we have never seen who shares his Potions and Care of Magical Creatures classes.
Snape, too, was looking at Harry in an unexpected way: It was a shrewd and calculating look, and Harry didn't like it.
As an ex-Death Eater in this era between the first and second wars against Voldemort, hearing someone speak Parseltongue must have been quite a shock for Snape, but he's handling his reactions quite well.
Exceptional character moments
Ernie, taking steps to protect Justin Finch-Fletchley against the perceived danger from Harry.
"You know what, Harry? If he doesn't stop trying to save your life he's going to kill you." [Ron on Dobby]
Deliberately causing mayhem in Snape's class was about as safe as poking a sleeping dragon in the eye.
Harry wondered why Lockhart was still smiling; if Snape had been looking at him like that he'd have been running as fast as he could in the opposite direction.