Chapter 86: Multiple Hypothesis Testing (2/2)

"Perhaps that is true," said the Potions Master from where he was lurking. "But what of it, Mad-Eye? Whatever his identity, Monroe was surely the Dark Lord's enemy. I've heard Death Eaters curse his name even after they thought him dead. They feared him well."

"So far as Defense Professors are concerned," Professor McGonagall said primly, "I shall take it and be grateful."

Moody swung around to glare at her. "Just where the devil was 'Monroe' all those years he was gone, eh? Maybe he thought he could make a name for himself in Britain by opposing Voldie, and vanished away when he found out he was wrong. Then why'd he come back now, hah? What's his new plan?"

"He, ah..." Harry ventured tentatively. "He says he always wanted to be a great Defense Professor because all the best fighting wizards have taught at Hogwarts. And he kind of is being an incredibly good Defense Professor, actually... I mean, if he just wanted to keep up a disguise, he could get away with much sloppier work..."

Professor McGonagall was nodding firmly.

"Naive," Moody said flatly. "I suppose you all haven't wondered if your Defense Professor set up the whole House of Monroe to be wiped out?"

"What?" cried Professor McGonagall.

"Our mystery wizard hears about a missing kid from a Most Ancient House of Britain," Moody said. "Steps into the shoes of 'David Monroe', but stays away from the real Monroe family. But eventually the House is bound to notice something wrong. So this imposter somehow prods Voldie into wiping them all out - maybe leaked a password they'd given him for their wards - and then he was a Lord of the Wizengamot!"

There seemed to be a fight going on inside Harry's mind between Hufflepuff One, who'd never trusted the Defense Professor in the first place; and Hufflepuff Two, who was far too loyal to Harry's friend, Professor Quirrell, to believe something like that just because Moody said so.

It is kind of obvious, though, observed his Slytherin part. I mean, do you actually believe that under natural circumstances, anyone would end up as the last heir to a Most Ancient House AND Lord Voldemort killed his family AND he has to avenge his martial arts sensei? If anything I'd say he went too far over the top in setting up his new identity as the ideal literary hero. That sort of thing doesn't happen in real life.

This from an orphan who was raised unaware of his heritage, commented Harry's Inner Critic. With a prophecy about him. You know, I don't think we've ever read a story about two equally destined heroes competing to see who's cliched enough to take down the villain -

Yes, replied the central Harry over the distant vroop-ing noise in the background, it's a very sad life we lead and YOU'RE NOT HELPING.

There's only one thing to do at this point, said Ravenclaw. And we all know what it is, so why argue?

But, Harry replied, how do we test experimentally whether or not Professor Quirrell is the original David Monroe? I mean, what sort of observable behaves differently, depending on whether he's the real David Monroe or an impostor?

"What do you want me to do about it, Mad-Eye?" Professor McGonagall was demanding. "I can't -"

"You can," the scarred man said, glaring at her fiercely. "Just fire the bloody Defense Professor."

"You say that every year," said Professor McGonagall.

"Yes, and I'm always right!"

"Constant vigilance or no, Alastor, the students must be taught!"

Moody snorted. "Pfah! I swear the curse gets worse every year, as you lot get more and more reluctant to let them go. Your precious Professor Quirrell would have to be Grindelwald in disguise, to get himself sent off!"

"Is he?" Harry couldn't help asking. "I mean, could he actually be -"

"I check Grindie's cell every two months," Moody said. "He was there in March."

"Could the person in the cell be a ringer?"

"I administer a blood test for his identity, son."

"Where do you keep the blood you use as a reference?"

"In a safe place." Something like a smile was stretching the scarred lips. "Have you considered the Auror Office after you graduate?"

"Alastor," Professor McGonagall said reluctantly. "The Defense Professor does have a... health condition. I suppose you will call it suspicious in itself - but it is by no means certain that it will be any ill-doing on his part which prevents us from renewing his employment."

"Yes, his little naptimes," Moody said darkly. "Amelia thinks he stepped into the path of a high-level curse. Sounds to me more like a Dark ritual gone wrong!"

"You've no proof of that!" Professor McGonagall said.

"That man might as well be wearing a sign saying 'Dark Wizard' in glowing green letters over his head."

"Ah..." Harry said. It didn't seem like an especially good time to ask what Mr. Moody thought of the 'not all sacrificial rituals are evil' standpoint. "Excuse me, but you said earlier that Professor Quirrell - I mean the old David Monroe - I mean the Monroe from the seventies - anyway, you said that person used the Killing Curse. What does that imply? Does somebody have to be a Dark Wizard to use it?"

Moody shook his head. "I've used it myself. All it takes is power and a certain mood." The grimacing lips were showing teeth. "The first time I cast it was against a wizard named Gerald Grice, and you can ask me what he did after you graduate Hogwarts."

"But why is it Unforgiveable, then?" Harry said. "I mean, a Cutting Hex can kill someone too. So why's it any better to use a Reducto instead of Avada Kedav-"

"Shut your mouth!" Moody said sharply. "Someone might take it the wrong way, your saying that incantation. You look too young to cast it, but there's such a thing as Polyjuice. And to answer your question, boy, there's two reasons why that spell's in the blackest book. The first is that the Killing Curse strikes directly at the soul, and it'll just keep going until it hits one. Straight through shields. Straight through walls. There's a reason why even Aurors fighting Death Eaters weren't allowed to use it before the Monroe Act."

"Ah," said Harry. "That does seem like an excellent reason to ban -"

"I'm not finished, son. The second reason is that the Killing Curse doesn't just take a powerful bit of magic. You've got to mean it. You've got to want someone dead, and not for the greater good, either. Killing Grice didn't bring back Blair Roche, or Nathan Rehfuss, or David Capito. It wasn't for justice, or to stop him doing it again. I wanted him dead. You understand now, lad? You don't have to be a Dark Wizard to use that spell - but you can't be Albus Dumbledore, either. And if you're arrested for killing with it, there's no possible defense."

"I... see," murmured the Boy-Who-Lived. You can't want the person dead as an instrumental value on the way to some positive future consequence, you can't cast it if you believe it's a necessary evil, you have to actually want them dead for the sake of being dead, as a terminal value in your utility function. "A magically embodied preference for death over life, striking within the plane of pure life force... that does sound like a difficult spell to block."

"Not difficult," Moody snapped. "Impossible."

Harry nodded gravely. "But David Monroe - or whoever - used the Killing Curse against a couple of Death Eaters even before they wiped out his family. Does that mean he already had to hate them? Like, the martial arts story was probably true?"

Moody shook his head slightly. "One of the dark truths of the Killing Curse, son, is that once you've cast it the first time, it doesn't take much hate to do it again."

"It damages the mind?"

Again Moody shook his head. "No. It's the killing that does that. Murder tears the soul - but that's just the same if it's a Cutting Hex. The Killing Curse doesn't crack your soul. It just takes a cracked soul to cast." If there was a sad expression on the scarred face, it could not be read. "But that doesn't tell us much about Monroe. The ones like Dumbledore who'll never be able to cast the Curse all their lives, because they never crack no matter what - they're the rare ones, very rare. It only takes a little cracking."

There was a strange heavy feeling in Harry's chest. He'd wondered what exactly it had meant, that Lily Potter had tried to cast the Killing Curse at Lord Voldemort with her last breath. But surely it was forgiveable, it was right and proper for a mother to hate the Dark Wizard who was coming to kill her baby, mocking her for how she couldn't stop him. There was something wrong with you as a parent if you couldn't cast Avada Kedavra, in that situation. And no other spell could've gone past the Dark Lord's shields; you'd have to at least try to hate the Dark Lord enough to want him dead for the sake of dead, if that was the only way to save your baby.

It only takes a little cracking...

"Enough," said Professor McGonagall. "What would you have us do?"

Moody's smile twisted. "Get rid of the Defense Professor and see if all your troubles mysteriously clear up. Bet you a Galleon they do."

Professor McGonagall looked like she was in pain. "Alastor - but - will you teach the classes, if -"

"Ha!" said Moody. "If I ever say yes to that question, check me for Polyjuice, because it's not me."

"I'll test it experimentally," Harry said. And then, as everyone looked at him, "I'll ask Professor Quirrell a question that the real David Monroe would know - like who else was in the Slytherin class of 1945, or something like that - hopefully without making it obvious. It won't be definitive proof, he could've studied the role, but it would be evidence. Still, Mr. Moody, even if Professor Quirrell isn't the original Monroe, I'm not sure that getting rid of him is a free action. He saved my life twice -"

"What?" demanded Moody. "When? How?"

"Once when he knocked down a bunch of witches who were summoning me toward the ground, once when he figured out that the Dementor was draining me through my wand. And if Professor Quirrell wasn't the one who set up Draco Malfoy in the first place, then he saved Draco Malfoy's life, and things would be a lot worse if he hadn't. If the Defense Professor isn't behind it all - he's not someone we can afford to just get rid of."

Professor McGonagall nodded firmly.

Hypothesis: Severus Snape

(April 8th, 1992, 9:03pm)

Harry and Professor McGonagall now stood on the slowly turning stairs, turning without descending; or at least one Harry stood upon those stairs - his other three selves had been left behind in the Headmaster's office.

"Can I ask you a private question?" Harry said, when he thought they were far enough away not to be heard. "And in particular, private from the Headmaster."

"Yes," Professor McGonagall said, not quite sighing. "Though I hope you realize that I cannot do anything which conflicts with my duties to -"

"Yes," Harry said, "that's exactly what I need to ask you about. In front of the Wizengamot, when Lucius Malfoy was saying that Hermione was no part of House Potter and that he wouldn't take the money, you told Hermione how to swear that oath. I want to know, if something like that comes up again, if your first duty is to the Hogwarts student Hermione Granger, or to the head of the Order of the Phoenix, Albus Dumbledore."

Professor McGonagall looked like someone had hit her in the face with a cast-iron frying-pan, a few minutes earlier, and now she'd been told that somebody was about to do it again, and not to flinch.

Harry flinched a little himself. Somewhere along the line he needed to pick up the knack of not phrasing things to hit as hard as he possibly could.

The walls rotated around them, behind them, and somehow, they descended.

"Oh, Mr. Potter," Professor McGonagall said with a low exhalation. "I... wish you wouldn't ask me such questions... oh, Harry, I wasn't thinking then, not at all. I only saw a chance to help Miss Granger and... I was Sorted into Gryffindor, after all."

"You've got a chance to think now," Harry said. It was all coming out wrong, but he had to say it anyway, because - "I'm not asking you to be loyal to me. But if you do know - if you are sure - what you'll do if it comes down to an innocent Hogwarts student versus the Order of the Phoenix a second time..."

But Professor McGonagall shook her head. "I'm not sure," the Transfiguration Professor whispered. "I don't know if it was the right choice even then. I'm sorry. I can't decide such awful things!"

"But you'll do something if it happens again," Harry said. "Indecision is also a choice. You can't just imagine having to make an immediate decision?"

"No," Professor McGonagall said, sounding a little stronger; and Harry realized that he'd accidentally offered a way out. The Professor's next words confirmed Harry's fears. "Such a dreadful choice as that, Mr. Potter - I think I should not make it until I must."

Harry gave an internal sigh. He supposed he had no right to expect Professor McGonagall to say anything else. In a moral dilemma where you lost something either way, making the choice would feel bad either way, so you could temporarily save yourself a little mental pain by refusing to decide. At the cost of not being able to plan anything in advance, and at the cost of incurring a huge bias toward inaction or waiting until too late... but you couldn't expect a witch to know all that. "All right," Harry said.

Though it wasn't right at all, not really. Dumbledore might want that debt removed, Professor Quirrell would also want Harry out of that debt. And if the Defense Professor was David Monroe, or could convincingly appear to be David Monroe, then Lord Voldemort technically hadn't exterminated the House of Monroe. In which case somebody might be able to pass a Wizengamot resolution revoking the Noble status of House Potter, which had been granted for avenging the Most Ancient House of Monroe.

In which case Hermione's vow of service to a Noble House might be null and void.

Or maybe not. Harry didn't know anything about the legalities, especially not whether House Potter got the money back if someone managed to send Hermione to Azkaban. Just because you lost something might not mean the payment was returned, legally speaking. Harry wasn't sure and he didn't dare ask a magical solicitor...

...it would have been nice to be able to trust at least one adult to take Hermione's side instead of Dumbledore's, if an issue like that threatened to come up.

The stairs they were upon ceased rotating, and they were before the backs of the great stone gargoyles, which rumbled aside, revealing the hallway.

Harry stepped out -

A hand caught at Harry's shoulder.

"Mr. Potter," Professor McGonagall said in a low voice, "why did you to tell me to keep watch over Professor Snape?"

Harry turned around again.

"You told me to keep watch, and see if he'd changed," Professor McGonagall went on, her tone urgent. "Why did you say that, Mr. Potter?"

It took a moment, at this point, for Harry to think back and remember why he had said that. Harry and Neville had rescued Lesath Lestrange from bullies, and then Harry had confronted Severus in the hallway and, at least according to the Potions Master's own words, 'almost died' -

"I learned something that made me worry," Harry said after a moment. "From someone who made me promise not to tell anyone else." Severus had made Harry swear that their conversations wouldn't be shared with anyone, and Harry was still bound by it.

"Mr. Potter -" began Professor McGonagall, and then exhaled, the flash of sharpness disappearing as quickly as it had come. "Never mind. If you cannot say, you cannot say."

"Why do you ask?" Harry said.

Professor McGonagall seemed to hesitate -

"All right, let me be more specific," Harry said. After Professor Quirrell had done it to him several times, Harry was starting to get the hang of it. "What change have you already observed in Professor Snape that you're trying to decide whether to tell me about?"

"Harry -" the Transfiguration Professor said, and then closed her mouth.

"I obviously know something you don't," Harry said helpfully. "See, this is why we can't always put off trying to decide our awful moral dilemmas."

Professor McGonagall closed her eyes, drew in a deep breath, pinched the bridge of her nose and squeezed it several times. "All right," she said. "It's a subtle thing... but worrying. How can I put this... Mr. Potter, have you read many books that young children are not meant to read?"

"I've read all of them."

"Of course you have. Well... I don't quite understand it myself, but for so long as Severus has been employed in this school, stalking about in that awful stained cloak, there has been a certain sort of girl that stares at him with longing eyes -"

"You say that like it's a bad thing?" Harry said. "I mean, if there's one thing I did understand from those books, it's that you're not supposed to question people's preferences."

Professor McGonagall gave Harry a very strange look.

"I mean," Harry said again, "from what I've read, when I'm a bit older there's something like a 10% chance that I'll find Professor Snape attractive, and the important thing is for me to just accept whatever I -"

"In any case, Mr. Potter, Severus has always been entirely indifferent to the stares of those young girls. But now -" Professor McGonagall seemed to realize something, and hastily said, her hands rising in warding, "Please don't mistake me, Professor Snape certainly has not taken advantage of any young witches! Absolutely not! He has never even so much as smiled at one, not that I ever heard. He has told the young girls to stop gaping at him. And if they stare at him regardless, he looks away. That I have seen with my own eyes."

"Er..." Harry said. "Sorry, but just because I've read those books doesn't mean I understood them. What does all that mean?"

"That he is noticing," Professor McGonagall said in a low voice. "It is a subtle thing, but now that I have seen it, I am certain. And that means... I am very much afraid... that the bond which held Severus to Albus's cause... may have weakened, or even broken."

2 + 2 = ...

"Snape and Dumbledore?" Then Harry heard the words that had just come out of his mouth, and hastily added, "Not that there's anything wrong with that -"

"No!" said Professor McGonagall. "Oh, for pity's sake - I can't explain it to you, Mr. Potter!"

The other shoe finally dropped.

He was still in love with my mother?

This seemed somewhere between beautifully sad, and pathetic, for around five seconds before the third shoe dropped.

Of course, that was before I gave him my helpful relationship advice.

"I see," Harry said carefully after a few moments. There were times when saying 'Oops' didn't fully cover it. "You're right, that's not a good sign."

Professor McGonagall put both hands over her face. "Whatever you're thinking right now," she said in a slightly muffled voice, "which I assure you is also wrong, I don't want to hear about it, ever."

"So..." Harry said. "If, like you said, the bond that held Professor Snape to the Headmaster has broken... what would he do then?"

There was a long silence.

What would he do then?

Minerva lowered her hands, gazing down at the upturned face of the Boy-Who-Lived. One simple question shouldn't have caused her so much dismay. She'd known Severus for years; the two of them bound, in some strange way, by the prophecy they'd both heard. Though Minerva suspected, from what she knew of the rules of prophecy, that she had only overheard it herself. It had been Severus's acts which had brought about the prophecy's fulfillment. And the guilt, the heartbreak which had come of that choice, had been tormenting the Potions Master for years. She couldn't imagine who Severus would be without it. Her mind went blank, trying to imagine; her thoughts an empty parchment.

Surely Severus was no longer the man he'd once been, that angry and terribly foolish young man who'd brought the prophecy before Voldemort in exchange for being admitted into the Death Eaters. She'd known him for years, and surely Severus was no longer that man...

Did she really know him at all?

Had anyone ever seen the real Severus Snape?

"I don't know," Professor McGonagall finally said. "I truly don't know at all. I can't even imagine. Do you know anything of this, Mr. Potter?"

"Er..." Harry said. "I think I can say that my own evidence points in the same direction as yours. I mean, it increases the probability that Professor Snape isn't in love with my mother anymore."

Professor McGonagall closed her eyes. "I give up."

"I don't know of anything wrong he's done apart from that, though," Harry added. "I assume the Headmaster cleared you to ask me about this?"

Professor McGonagall looked away from him, staring at the wall. "Please don't, Harry."

"All right," Harry said, and turned and hurried out into the hallways, hearing Professor McGonagall more slowly walking after, and the rumbling sound of the gargoyles moving into place.

It was the morning after next, during Potions class, that Harry's potion of cold resistance boiled over his cauldron with a green froth and mildly nauseating smell, and Professor Snape, looking more resigned than disgusted, told Harry to stay after class. Harry had his own suspicions about this affair, and as soon as class let out - Hermione, as usual for the last few days, being the first to flee out the door - the door swung shut and locked behind the departing students.

"I apologize for ruining your potion, Mr. Potter," Severus Snape said quietly. There was upon his face the strange sad look that Harry had seen only once before, in a hallway some time ago. "It will not be reflected in your grades. Please, sit down."

Harry sat back down at his desk, filling up the time by scrubbing a bit more at the green stain on the wooden surface, as the Potions Master incanted a few privacy spells.

When the Potions Master was done, he spoke again. "I... do not know how to broach this topic, Mr. Potter, so I will simply say it... before the Dementor, you recovered your memory of the night your parents died?"

Harry silently nodded.

"If... I know it must not be a pleasant memory, but... if you could tell me what happened...?"

"Why?" Harry said. His voice was solemn, definitely not mocking the pleading look that Harry had never expected to see from that person. "I wouldn't think that would be a pleasant thing for you to hear either, Professor -"

The Potions Master's voice was almost a whisper. "I have imagined it every night these last ten years."

You know, said Harry's Slytherin side, it might not be such a good idea to give him closure, if his guilt-based loyalties are already wavering -

Shut up. Overruled.

It wasn't something that Harry could actually bring himself to deny. He took one suggestion from his Slytherin side, and that was it.

"Will you tell me exactly how you came to learn about the Prophecy?" Harry said. "I'm sorry to make this a trade, I will tell you afterward, only, it could be really important -"

"There is little to say. I had come to be interviewed by the Deputy Headmistress for the position of Potions Master, and so I was waiting outside the room of the Hog's Head Inn when the applicant before me, Sybill Trelawney, came to seek the position of Professor of Divination. As soon as Trelawney finished speaking her words, I fled, forsaking my chance at Hogwarts's Mastery, and went to the Dark Lord." The Potions Master's face was drawn and tight. "I did not even pause to consider why that riddle might have come to me, before I sold it to another."

"A job interview?" Harry said. "Where you and Professor Trelawney both happened to be applying, and Professor McGonagall was interviewing? That seems... like rather a large coincidence..."

"Seers are the pawns of time, Mr. Potter. Coincidence is beneath them, and they are above it. I was the one meant to hear that prophecy and become its fool. Minerva's presence made no final difference to how it came about. There was no Memory Charm as you supposed, I do not know why you thought that, but there was no Memory-Charm, there could have been no Memory-Charm. The voice of a seer has a quality, an enigma which even Legilimency cannot share, how could that be imbued in a false memory? Do you think the Dark Lord would believe my mere words? The Dark Lord seized my mind and saw the mystification there, even if he could not seize the mystery, and so he knew the prophecy had been true. The Dark Lord could have killed me then, having taken what he wanted - I was a fool indeed to go to him - but he saw something in me I do not know, and took me into the Death Eaters, though on his terms rather than mine. That is how I brought it about, brought it all about, from beginning to end, always my own doing." Severus's voice had gone rather hoarse, and his face was filled with naked pain. "Now tell me, please, how did Lily die?"

Harry swallowed twice, and began his recounting.

"James Potter shouted for Lily to run away with me, that he would hold off You-Know-Who."

"You-Know-Who said -" Harry stopped, the chills going all over his own skin, his own muscles tightening as if in preparing for a seizure. The memory was returning strongly, now, accompanied by cold and darkness in association. "He used... the Killing Curse... and then he came upstairs somehow, I think he must have flown, I don't remember any footsteps on stairs or anything like that... and then my mother said, 'No, not Harry, please not Harry!' or something like that. And the Dark Lord - his voice was so high, like water whistling out of a teakettle only cold - the Dark Lord said -"

Stand aside, woman! For you I am not come, only the boy.

The words were very clear in Harry's memory.

"- he told my mother to get out of his way, that he was only there for me, and my mother begged him to have mercy, and the Dark Lord said -"

I give you this rare chance to flee.

"- that he was being generous and giving her a chance to run, but he wouldn't bother fighting her, and even if she died, she couldn't save me -" Harry's voice was unsteady, "- and so she ought to get out of his way. And that was when my mother begged the Dark Lord to take her life instead of mine - and the Dark Lord - the Dark Lord said to her - and his voice was lower this time, like he was dropping a pose -"

Very well, I accept the bargain.

"- he said that he accepted her offer, and that she should drop her wand so he could kill her. And then the Dark Lord waited, just waited. I, I don't know what Lily Potter was thinking, it hadn't even made sense in the first place, what she said, it wasn't like the Dark Lord would kill her and then just leave, when he'd come there for me. Lily Potter didn't say anything, and then the Dark Lord started laughing at her and it was horrible and - and she finally tried the only thing left that wasn't abandoning me or just giving up and dying. I don't know if she even could've, if the spell would've worked for her, but when you think about, she had to try. The last thing my mother said was 'Avada Ke-' but the Dark Lord started his own curse as soon as she said 'Av' and he said it in less than half a second and there was a flash of green light and then - and then - and then -"

"That's enough."

Slowly, like a body floating to the surface of water, Harry returned from wherever he'd been.

"That's enough," the Potions Master said hoarsely. "She died... Lily died without pain, then? The Dark Lord... did not do anything to her, before she died?"

She died thinking that she'd failed, and that the Dark Lord was going to kill her baby next. That's pain.

"He - the Dark Lord didn't torture her -" Harry said. "If that's what you're asking."

Behind Harry, the door unlocked itself and swung open.

Harry left.

It was Friday, April 10th, of 1992.