Hermione breaks it to Harry: "Umbridge has been reading your mail, Harry. There's no other explanation" (18.1).
Hermione thinks it was Professor Umbridge who told Filch Harry was ordering a large quantity of Dungbombs. It was just an excuse to get access to his mail.
At least Angelina has gotten permission to start up the Gryffindor Quidditch team again.
That night at 7:00 PM, Ron and Harry go down to the Quidditch pitch for practice.
It's pouring rain.
The practice is miserable and sodden.
After practice, Harry's scar starts to ache suddenly.
Harry tells Ron, "[Voldemort's] probably miles away. It hurt ... because ... he's angry" (18.84).
Ron looks horrified – Harry seems to be reading Voldemort's mind.
When his scar ached in Professor Umbridge's office, it was because Voldemort was "pleased [...] Really pleased. He thought ... something good was going to happen. And the night before [Harry] came back to Hogwarts [...] he was furious" (18.97).
Ron tells Harry he has to tell someone about this. Dumbledore would want to know.
But Harry stays stubborn.
As Harry tries to study for Charms, he keeps getting distracted by other thoughts.
Finally, he dozes off.
Harry dreams of a windowless corridor with a door at the end of it. Harry wants to get through that door desperately.
Dobby the house-elf wakes Harry out of this dream.
Dobby has come to return Harry's owl. Professor Grubbly-Plank says Hedwig is better now.
Dobby is wearing layers and layers of knitted things.
It turns out that it's Dobby and Winky (see Book Four) who have been taking all of Hermione's hats and gloves.
Winky is still depressed about being freed: "She still does not care for clothes" (18.145), observes Dobby.
In fact, none of the house-elves care for clothes: "None of them will clean Gryffindor Tower any more, not with the hats and socks hidden everywhere, they finds them insulting, sir" (18.145)
Harry asks Dobby if he knows of a place where 28 people can practice Defense Against the Dark Arts in secret.
Dobby does know a place: the Come and Go Room, a.k.a. the Room of Requirement.
This is a special room that can only be entered if a person has real need. So, "Dobby has used it [...] when Winky has been very drunk; he has hidden her in the Room of Requirement and he has found antidotes to Butterbeer there, and a nice elf-sized bed to settle her on while she sleeps it off" (18.158).
Harry asks Dobby to tell him exactly where the Room of Requirement is and how to get there.
Harry, Ron, and Hermione spend the day tracking down people to let them know where and when the meeting will be.
When the Room of Requirement appears, it is "lined with wooden bookcases and instead of chairs there were large silk cushions on the floor. A set of shelves at the far end of the room carried a range of instruments such as Sneakoscopes, Secrecy Sensors, and a large, cracked Foe Glass that Harry was sure had hung, the previous year, in the fake Moody's office" (18.190).
A lot of people start coming in: Ginny, Neville, Lavender, Parvati, Dean, Fred, George, Cho Chang, and all the others.
Hermione wants to elect a leader of the group.
Cho nominates Harry and everyone agrees.
They decide to call the group the DA. Cho wants it to stand for "Defense Association," but Ginny prefers "Dumbledore's Army," since that's what the Ministry of Magic is afraid of.
Harry splits everyone into pairs and starts teaching them Expelliarmus, the Disarming Charm.
Harry moves through the room giving pointers. Slowly, people start to get the hang of it.
When Harry comes around to watch Cho Chang, she suddenly sets her friend Marietta's sleeve on fire.
Harry says it was lousy, "but I know you can do it properly, I was watching from over there" (18.241).
Cho laughs. She tells Harry her parents have "forbidden [her] to get on the wrong side of Umbridge" (18.245) but she wants to keep fighting because of what happened to Cedric (her ex-boyfriend).
An awkward silence falls.
Luna pipes up, "my dad is very supportive of any anti-Ministry action" (18.247).
The lesson wraps up and they agree to meet again the following Wednesday.
Hermione is delighted with how the lesson has gone.
And Harry is distracted by the news that he makes Cho nervous.