"Am I supposed to just believe that?"
"You can ask Professor Quirrell if you don't believe me," said Harry. "Ask him whether Harry Potter can cast a corporeal Patronus, and tell him that I told you to ask. He'd know the request was from me, no one else would know."
Oh, and now Draco was to trust Professor Quirrell? Still, knowing Harry, it might be true; and Professor Quirrell wouldn't lie for trivial reasons.
The glowing snake turned its head back and forth, as though seeking a prey that wasn't there, and then coiled itself into a circle, as though to rest.
"I wonder," Harry said softly, "when it was, which year, which generation, that Slytherins stopped trying to learn the Patronus Charm. When it was that people started to think, that Slytherins themselves started to think, that being cunning and ambitious was the same as being cold and unhappy. And if Salazar knew that his students didn't even bother showing up to learn the Patronus Charm any more, I wonder, would he wish that he'd never been born? I wonder how it all went wrong, when Slytherin's House went wrong."
The shining creature winked out, the turmoil rising in Draco making it impossible to sustain the Charm. Draco spun on Harry, he had to control himself not to raise his wand. "What do you know about Slytherin House or Salazar Slytherin? You were never Sorted into my House, what gives you the right to -"
And that was when Draco finally realized.
"You did get Sorted into Slytherin!" Draco said. "You did, and afterwards you, you somehow, you snapped your fingers -" Draco had once asked Father if it would be cleverer to get Sorted into some other House so that everyone would trust him, and Father had smiled and said that he'd thought of that too at Draco's age, but there was no way to fool the Sorting Hat...
...not until Harry Potter came along.
How had he ever bought for one minute that Harry was a Ravenclaw?
"An interesting hypothesis," Harry said equably. "Do you know, you're the second person in Hogwarts to come up with a theory along those lines? At least you're the second that's actually said so to my face -"
"Snape," Draco said with certainty. His Head of House was no fool.
"Professor Quirrell, of course," said Harry. "Though come to think, Severus did ask me how I managed to stay out of his House, and whether I had something the Sorting Hat wanted. I suppose you could say you're number three. Oh, but Professor Quirrell's theory was a little different than yours, though. May I have your word not to repeat it?"
Draco nodded without even really thinking about it. What was he supposed to do, say no?
"Professor Quirrell thought that Dumbledore wasn't happy with the Hat's choice for the Boy-Who-Lived."
And the instant Harry said it, Draco knew, he knew that it was true, it was just obvious. Who did Dumbledore even think he was fooling?
...well, besides every single other person in Hogwarts except Snape and Quirrell, Harry might even believe it himself...
Draco stumbled back over to his desk in something of a daze, and sat down hard enough to hurt slightly. This sort of thing happened around once a month with Harry, and it hadn't happened yet in January, so it was time.
His fellow Slytherin, who might or might not think himself a Ravenclaw, sat back down in the chair he'd used earlier, now sitting on it crosswise, and looking up intently at Draco.
Draco didn't know what he should be doing now, whether he should be trying to persuade the lost Slytherin boy that, no, he wasn't actually a Ravenclaw... or trying to figure out whether Harry was in league with Dumbledore, though that suddenly seemed less likely... but then why had Harry set up the whole thing with him and Granger...
He really should have remembered that Harry was too weird for any normal plots.
"Harry," Draco said. "Did you deliberately antagonize me and General Sunshine just so we'd work together against you?"
Harry nodded without hesitation, as though it was the most normal thing in the world, and nothing to be ashamed of.
"The whole thing with the gloves and making us climb up the walls of Hogwarts, the only point was to make me and Granger more friendly toward each other. And even before then. You've been plotting it for a really long time. Since the beginning."
Again the nod.
"WHYYYYY?"
Harry's eyebrows lifted for a moment, the only reaction he showed to Draco shrieking so loudly in the closed classroom that it hurt his own ears. WHY, WHY, WHY did Harry Potter DO this sort of thing...
Then Harry said, "So that Slytherins will be able to cast the Patronus Charm again."
"That... doesn't... make... SENSE!" Draco was aware that he was losing control of his voice, but he didn't seem able to stop himself. "What does that have to do with Granger?"
"Patterns," Harry said. His face was very serious now, and very grave. "Like a quarter of children born to Squib couples being wizards. A simple, unmistakable pattern you would recognize instantly, if you knew what you were looking at; even though, if you didn't know, you wouldn't even realize it was a clue. The poison in Slytherin House is something that's been seen before in the Muggle world. This is an advance prediction, Draco, I could have written it down for you before our first day of school, just from hearing you talk in King's Cross Station. Let me describe some really pathetic sorts of people that hang around at your father's political rallies, pureblood families that would never be invited to dinner at Malfoy Manor. Bearing in mind that I've never met them, I'm just predicting it from recognizing the pattern of what's happening to Slytherin House -"
And Harry Potter proceeded to describe the Parkinsons and Montagues and Boles with a calmly cutting accuracy that Draco wouldn't have dared think to himself in case there was a Legilimens around, it was beyond insult, they would kill Harry if they ever heard...
"To sum up," Harry finished, "they don't have any power themselves. They don't have any wealth themselves. If they didn't have Muggleborns to hate, if all the Muggleborns vanished the way they say they want, they'd wake up one morning and find they had nothing. But so long as they can say purebloods are superior, they can feel superior themselves, they can feel like part of the master class. Even though your father would never dream of inviting them to dinner, even though there's not one Galleon in their vaults, even if they did worse on their OWLs than the worst Muggleborn in Hogwarts. Even if they can't cast the Patronus Charm any more. Everything is the Muggleborns' fault to them, they have someone besides themselves to blame for their own failures, and that makes them even weaker. That's what Slytherin House is becoming, pathetic, and the root of the problem is hating Muggleborns."
"Salazar Slytherin himself said that mudbloods needed to be cast out! That they were weakening our blood -" Draco's voice had risen to a shout.
"Salazar was wrong as a question of simple fact! You know that, Draco! And that hatred is poisoning your whole House, you couldn't cast the Patronus Charm using a thought like that!"
"Then why could Salazar Slytherin cast the Patronus Charm?"