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?"