Harry Potter and the Methods of Rationality

A jolt of adrenaline went through Hermione, she was instantly drawing her wand and spinning around -

But she couldn't see anything wrong, through the greater blue haze now surrounding them all.

The other girls, who had likewise pulled into formation, were also looking puzzled.

"Sorry!" said Susan. "Sorry, girls. Give me a moment to check this place out. Thinking of a certain person has just reminded me that this hall we're in right now, with all those doors, would be an excellent place for an ambush."

There was a moment of silence.

"Now," said a harsh male voice, blurred into unidentifiability by a buzzing undertone.

All six sets of double doors slammed open.

White robes filed silently forward, all-concealing white robes without marks of House affiliation and white cloth hiding the faces beneath the hoods. They marched out, and marched out, crowding the great corridor in numbers too high to count easily. Less than fifty robes, probably. Certainly more than thirty. All of them already surrounded by blue haze.

Susan said some Extremely Bad Words, so awful that at almost any other time, Hermione would have noticed.

"That message!" Daphne cried in sudden horror. "It wasn't from -"

"Millicent Bulstrode?" said the voice and its buzzing undertone. "No, it wasn't. You see, Miss Greengrass, if the same girl sends off a Slytherin message every day you fight a bully, pretty soon someone else will notice. We'll have a talk with her after we're done with you."

"Miss Susan," said Hannah in a voice just starting to quaver, "can you be super enough to -"

Wands rose in many hands. There came a series of blinding flashes of green light, a massive volley of shieldbreakers, at the end of which there was no more protective blue dome surrounding them, and Susan had fallen to her knees, clutching her head.

Barriers of solid blackness had sprung into being at both ends of the corridor. Behind the double doors that Hermione could see into, there were only unused classrooms, very dead ends.

"No," said the male voice with that buzz overlaid, "she can't. In case you haven't noticed, you've gotten quite a lot of people very angry at you and we have no intention of losing this time. All right everyone, prepare to fire."

The wands around the perimeter aimed again, low enough that their enemies wouldn't hit each other if they missed.

And then another male voice, with a similar buzz accompanying it, suddenly said "Homenum Revelio!"

An instant later there was another massive volley of shieldbreakers and hexes, fired on reflex at the suddenly revealed figure, shattering the shields which had almost immediately begun to form around it -

And then, as that same figure fell to the ground, a stunned silence.

"Professor Snape?" said the second voice. "He's the one who's been interfering?"

It was the Potions Master of Hogwarts who now lay unconscious on the stone floor, the dirt-spotted robes stirring for a final moment before they settled in place, his fallen hand outstretched toward where his wand was slowly rolling away.

"No," said the first male voice, now sounding a bit more uncertain. Then it rallied, "No, that can't possibly be it. He heard us passing the word, of course, and came along to make sure nobody screwed it up again. We'll wake him up afterward and apologize and he'll Memory-Charm the children so they don't remember, he's a Professor so he can do that. Anyway, we should make sure we're really alone now. Veritas Oculum!"

Fully two dozen different Charms must have been spoken, then, but no more invisible people showed up. One of them in particular made Hermione's heart sink; she recognized it as the Charm which had been listed alongside the description of the True Cloak of Invisibility, which would not reveal the Cloak, but would tell you whether it or certain other artifacts were nearby.

"Girls?" whispered Susan. She was slowly pushing herself to her feet, though Hermione could see her limbs swaying and quivering. "Girls, I'm sorry for what I said before. If you've got anything clever and heroic to try, you might as well try it."

"Oh, yeah," Tracey Davis said then, her voice trembling. "I almost forgot." The Slytherin girl raised her voice, and spoke.

"Hey, all of you!" yelled Tracey in a high-pitched shaky shout. "Hey, are you planning to hurt me too?"

"Yes, actually," said the buzzing voice of the leader. "We are."

"I'm under Harry Potter's protection, you know! Anyone who tries to hurt me will learn the true meaning of Chaos! So are you going to let me go?" It should have sounded defiant. It came out sounding terrified.

There was a pause. Some of the hoods of the robes turned to face each other, then turned back to face the girls.

"Hm..." said the buzzing male voice. "Hm... no."

Tracey Davis put her wand away into her robes.

Slowly, deliberately, she raised her right hand high in the air, and pressed her thumb and forefingers together.

"Go ahead," said that voice.