The rest of the teachers arrived sometime in the late morning of September 1st, and Ed knew this because they all dropped by the classroom that he and Dobby were setting up.

Ed hadn't expected to enjoy this part of the job so much, but in hindsight, he really should have; there was very little Ed liked more than telling people about alchemy. He'd spent most of the last week designing the curriculum and lesson plans, leaving enough room that people could miss a few here and there without getting completely lost. They still had actual classes, after all.

He didn't need a ton of stuff for the classroom. But he'd drawn by hand two large posters, one with a number of different base matrices and one with many of the simplest alchemical symbols, which Dobby was somehow attaching to the wall – given that the walls were stone, Ed assumed that he was using magic and not, like, tacks.

There were a couple of boxes, too, mostly full of chunks of granite or wood, and a big bucket of chalk. Dumbledore had assured him that he could ask for anything more specific should the need arise.

Ed really needed to figure out how magic worked with materials.

McGonagall was the first teacher to drop by – Deputy Headmistress, if he remembered right. She knocked politely on the door and came in when he shouted, and swept an assessing gaze over his classroom before her eyes landed on him, setting up the filing system by his desk. A shiver ran down his spine; something about her demeanor reminded him of Izumi.

"Good morning, Professor Elric," she said at last, inclining her head toward him. "I see you have located assistance in setting up your classroom."

"Yeah, it was Filius' idea," Ed confirmed, glancing over at where Dobby was squinting at the posters, adjusting them so they were perfectly aligned. "Dobby's been a pretty big help so far. Did you need something?"

"Albus hasn't shared with me why he went out of his way to bring you here," McGonagall informed him, "and I won't ask. But I would rather like to know your particular area of expertise."

"Huh." So it was that secret, or he didn't trust McGonagall that much? Ed had to wonder. "I'm an expert on biological alchemy. Making and unmaking chimeras, mostly." On paper, anyway. Even with all the research he'd done towards helping the survivors of the military's sick experiments, human bodies and souls were still his first and foremost expertise.

Her eyebrows rose. "How old are you?"

"Twenty," Ed said. "I'm a prodigy, which is weirdly harder for people to believe now that I'm not a kid anymore. But I passed Amestris' eminent alchemy test when I was twelve. And that was with alchemy from outside my specialty."

"Why would you do that?" McGonagall asked, stepping closer to examine the posters Dobby had finally left alone.

"Because I was a dumb kid, but not that dumb," Ed informed her. "Signing up to work for the Amestrian military as a biological alchemist? That's how you get blackmailed into committing war crimes." McGonagall frowned. "It's kind of what Amestrian alchemists are famous for. Open secret back home."

"Hm," McGonagall said, inscrutably, and then, "So Albus called you here in your capacity as an alchemist?"

Ed nodded. "As far as I know. I mean, back home I have a rep as a combat alchemist too, but..." He indicated his body. "Fucking wards made my prosthetics break down. But he didn't immediately send me home, so I assume that wasn't what he wanted from me."

"Did he at least offer?" McGonagall demanded, irritation flashing across her eyes. Ed shot her a quick, amused smile.

"I had the option," he assured her. "But I was pretty excited about this job, and it's not like I've never used a manual leg before. I wasn't gonna pass up magic over it." He shrugged. "It's just a school year."

"Pass up- Professor Elric, are you a Squib?" McGonagall asked, clearly astonished.

"What's a Squib?" Ed asked, glancing up from his files to frown at her. Her mouth opened a little.

"Are you a Muggle?" she almost squawked, and then cleared her throat. "Or does the Amestrian Wizarding World use different terms for non-magic children?"

"A Squib is a non-magic kid of magic parents?" Ed asked, curious whether he'd guessed right. McGonagall nodded, relaxing a little, so Ed popped her bubble by saying, "Dumbledore wasn't super clear. I'm not legally a Muggle, but I'm definitely not a wizard. Which, as far as I can tell, makes me a Muggle."

McGonagall blinked rapidly for a minute, and then nodded to herself firmly. "Then by all means, Professor Elric, feel free to ask any of your fellow staff for clarification, should anything become confusing. You must be quite intelligent indeed for Albus to go so far out of his way."

Ed's mouth curved, and he didn't bother denying it. It was true, after all.

So his first meeting with McGonagall went pretty well. The next teacher came in as he and Dobby were arranging the desks in the room, widening the gaps until a wheelchair could fit through. Ed was limping by then. His stumps were aching so badly that he was certain that it was going to rain later, and it was a relief when he finally dropped into his chair.

"You do not appear to me to be in a coma, Professor Elric."

Ed frowned and glanced over his shoulder. "You must be the potion guy," he said after a moment, studying the greasy-haired man. "Severus?"

"Quite," Snape said curtly, crossing the room to set a vial on the table. "And I remain curious as to why you have need for a potion that generally has to be fed in through a tube."

Ed snorted. "Well, it's not any of your business, but." He swallowed the potion, pulling a face at the sour, rotten flavor. "I'm short two twenty-pound steel prosthetics for the school year, and I want to be able to move them when I go home. If I let the muscles atrophy, that's gonna be, like, six months of reconditioning."

Snape's eyebrows lifted, and he glanced down at Ed's feet. "How unusual."

"Thanks," Ed said dryly, leaving it up to Snape to determine what for, and went back to listing things he wanted in his desk drawers.

Professor Sprout offered to show Ed the homicidal plants in the greenhouses. She was his favorite.

It was also Professor Sprout that led him to the Great Hall when it was nearly time for the students to arrive, and Ed couldn't help but bounce a little in anticipation. It had been a long damn time since he'd even been in a school, and now he was supposed to teach. Hell, the last teacher he'd had was Izumi.

He probably shouldn't follow her example.

Ed's seat turned out to be next to Professor Sprout's, so they were able to keep talking about the fantastically horrible little plants in her greenhouses, both still damp from the rain, and Ed shared some of his research on combining plants. He was pretty sure she didn't understand a word of it (not many did) but she listened indulgently anyway. Both of them ignored the commotion coming from outside the Great Hall, though McGonagall stood up and stormed toward the door.

The students started pouring in shortly afterward, most of them soaking wet. They flowed toward the four tables, slowly filling them up, and Ed cut off his rambling to watch the proceedings with interest. Sprout fell silent as well, though her expression was more indulgent than entranced.

The ghosts came in next. Ed hadn't seen more than a glimpse of them, for the most part – he'd been too preoccupied with all of the... everything else. But it was astonishing to see them all in one place, nearly a dozen of them, and he itched to find out how it was that they were still around.

Dumbledore conducted the ceremony with the ease of both long practice and great affection, one part flowing into the next. The singing hat, the announcements, the Sorting, and the feast were all treated with the same irreverent but genuine care. This was more than just a formality to Dumbledore, Ed could tell.

"Have you looked up yet, Professor Elric?" Sprout asked him quietly, and without thinking, Ed looked up.

Rain pattered against an invisible shield far above them, droplets disappearing as they hit, and he could see the stormclouds the castle was mired in. Ed felt himself smile without conscious thought, delighted.

The bang of a door made him jump, and he dropped his gaze in time to see a man limp inside, as drenched as anyone else. The dull clunk of wood on wood announced every other step, and Ed caught a glimpse of a clearly artificial foot before it disappeared back under his cloak as the man stomped steadily down the aisle.

"Ah, Alastor," Professor Sprout said with relief. "I was beginning to worry."

Ed stared at the man. Something was bothering him.

The man was limping. Heavily.

"Hey, how long has Alastor been missing that leg?" Ed asked Sprout, without looking away.

"Hm?" Sprout asked, surprised. "I'm afraid I really couldn't say. Certainly at least fifteen years. Twenty, perhaps."

Fifteen years, minimum. And he was hauling his leg like there was a ball-and-chain attached to the ankle.

Ed chose not to say anything, but he watched Alastor as the man walked up, dismissed Dumbledore's quiet inquiry, and stomped over to his seat. He drank deeply from a hip flask, and then dug into his food.

Ed shifted his gaze, but not his attention, away from the stranger, and listened to Dumbledore explain an old wizarding tradition that would be taking place this year. Ed wondered if it had been a coincidence that this was when he'd chosen to call Ed to Hogwarts, or if he'd hoped everyone would be too busy to take much note of his presence.

He'd talk to Dumbledore when everyone was dismissed.

It felt like an eternity before the last of the dishes finally cleared away. Ed stayed in place until Dumbledore stood up, and then immediately rose to his feet to follow him. Dumbledore gave him a small, amiable smile.

"What is it, Professor?" he asked kindly.

"You haven't told me the password to my rooms yet, remember?" Ed said, meeting his eyes evenly. "Anyway, I needed to talk to you about class."

Dumbledore's smile faded almost imperceptibly, but he played along. "Ah, of course. I am getting quite forgetful in my old age, aren't I? Come along, then."

Ed didn't say another word until they were climbing the awful steep stairs to Dumbledore's office, and then it was mostly to swear under his breath, keeping hold of the railing. Dumbledore followed his example, and stayed quiet until the door shut behind them. Then he turned around to frown at Edward, clear concern in his eyes.

"Is something the matter, Edward?"

Ed ground his teeth briefly, because it was hard to explain what he was worried about when most people didn't have the kind of background he did.

"Is there shapeshifting magic?" he asked abruptly. "Like- can someone look like someone else?"

Dumbledore's burgeoning amusement disappeared in a flash. "The Polyjuice Potion, yes. What concerns you?"

Ed rocked on his heels a little, reminded himself that he knew how prosthetics worked, and said, "That guy that walked in late... He doesn't know how to walk on a prosthesis."

Dumbledore furrowed his brow. "He was walking just fine, I thought."

"He was limping," Ed said. Dumbledore didn't react. Ed continued, a little impatiently, "Your friend, Kettleburn, did he walk with a limp? Do I walk with a limp? Dumbledore- have you ever seen this guy walk with a limp before today?"

There was the look of dawning realization Ed had been waiting for.

"No, I haven't," Dumbledore said quietly, and now he looked grim. "Alastor did not mention sustaining any injuries."

"Prosthetic legs are designed to carry your weight naturally," Ed informed him, wanting to really drive the point home. "Walking is more about controlled falls than picking up your feet and moving them, so you have to learn to trust your prosthetic to get the stride down. Pomona told me that Alastor lost that leg at least fifteen years ago. That guy, he was dragging it like an amateur. Either he wasn't properly trained, or that wasn't Alastor."

A few moments of heavy silence slipped by.

"Then I suppose there's no time to waste," Dumbledore said at last, quietly. He looked at one of the portraits above their heads. "Dilys, could you alert Minerva, please? Tell her to fetch Severus and meet me in Alastor's office in, oh, half an hour or so. They should consider bringing Veritaserum."

Ed took that to mean that Dumbledore was taking his concerns seriously.

Dumbledore gestured, and Ed turned around with a grunt, then headed back down the spiral steps to the next hall. "What're you thinking?"

"I can easily draw Alastor into conversation," Dumbledore said mildly. "So perhaps while I do that, you could examine his office. Polyjuice Potion is a rather unappealing substance, with the consistency and color of thick mud. But anything you find could be useful."

Ed smirked. "Sounds like a plan."

He lagged behind Dumbledore, and waited around the corner for the two men's voices to fade away before he headed for Alastor's office. He was glad for the excuse to poke around; there were dozens of mysterious devices that he would dearly love to know the purpose of, and a lot of them were making helpful noises that covered up any sound he made. There was a creepy mirror full of hazy faces.

In the right-hand drawer of the teacher's desk, Ed found a large flask and a funnel. The flask was full of thick, mud-colored goop. His mouth curved mirthlessly.

He left that out on the desk, clearly visible.

That, of course, gave him more than enough reason to start really digging through the office. He found some boring things: lesson plans, blank parchment, quills and ink. He also found a chest with seven locks, and a keyring with seven keys.

When he fit one of the keys into the seventh lock, it opened to reveal an alarmingly deep pit, and he had to go grab one of the candle-lit lamps to look inside. There was definitely a person in there; this far up, he couldn't tell if they were alive. He left the lid open, backed away, and kept searching.

Severus and Minerva ended up reaching the office before Dumbledore and the imposter got back, which was probably good for the plan, but distinctly inconvenient for Ed. When they arrived, he'd started digging through a few boxes that the imposter hadn't yet unpacked; that turned out to be where most of the weird noises were coming from.

"Elric, what are you doing?" Minerva demanded, which he supposed was a fair reaction to finding him rooting through the belongings of someone she believed to be, at the very least, an experienced and trustworthy veteran.

"Look at the desk," he said without looking up. An audible gasp followed almost immediately. "Yeah. Dumbledore's with the guy right now, playing distraction. You can go look for them if you want, I guess, but it'd probably be smarter to ambush him."

"Incredible," Severus drawled, crossing over to pick up the flask. "You have somehow managed to find trouble with a speed normally only Potter can replicate."

"That doesn't mean anything to me," Ed told the box he was digging through, and then, "Hell. Why did I tell you to look at the desk? Stupid. You should get that guy out of the chest. I think it's Alastor."

There was a small scuffle on the other side of the room, and another gasp, then a thud. Only a few minutes later, another thud. Ed glanced over his shoulder. Yep, there was Alastor.

"Ennervate," McGonagall murmured, and the man jerked awake with a choked snarl. "Alastor? Are you alright?"

Alastor swore frantically for a couple seconds, shoving himself away from Minerva, and Ed abandoned his task to turn around and watch. The man's one eye darted back and forth wildly for a minute, and then he looked over his shoulder, back at them, patted his pockets, then the stump of his leg.

"Son of a bitch!" Alastor roared at last. If Ed had had two hands, he would have clapped them over his ears. "Where is that bastard?"

"I'm informed that he's currently with Albus, who is distracting him while Professor Elric investigated your office," Minerva answered, a wry twist to her voice. "I'm afraid I'm not caught up on all the details myself."

"Elric?" The man's gaze jerked straight to him, squinty and suspicious. Which, yeah, Ed would be squinty and suspicious of strangers too, if he woke up missing both his prosthetics. "Who the hell are you? Why are you a part of this?"

"'Cause I'm the only one who noticed it wasn't you," Ed said plainly, squirming around until he was in a sitting position. Looked like they'd be here a while. As an afterthought, he added, "I'm doing a favor for Dumbledore. You can ask him about it later if you're curious."

"We've never met," Alastor snapped. Ed nodded.

"Yeah," he said, "but no guy that's had a prosthetic leg for fifteen years drags it behind him like it's made of rock."

Alastor's eye darted down to Ed's legs, and he nodded sharply. "Clever. Amateur move on the imposter's part." He looked back at Minerva. "How long has it been? How long since the start of the school year?"

"Not even a day, Alastor," Minerva said, giving Ed a sideways look that he thought might be a smile. "The spy chose to make his entrance in such a way that it... quite drew attention to his gait. Professor Elric left the feast with Albus, and it's been not an hour since."

For the first time, Alastor relaxed, just a little.

"Then one of you should intercept them before they return," Alastor said. "Specifically, before he sees all of you speaking to me, with my eye! That can see through walls!"

Without a word, Severus turned and swept out the door.

"Do you have a spare leg, or are we gonna have to pry it off the imposter?" Ed asked Alastor, since apparently no one else was going to.

"Toss me my keys," Alastor demanded. Minerva did, and Alastor shuffled over to the chest, opened the fourth compartment, and pulled out a leg. "Dated piece of garbage. But it's a leg."

He pulled it on, dug through his trunk again, and pulled out a knife.

"Not as good as a wand, but it'll do," Alastor muttered. "Underhanded yellow-bellied slack-jawed son of a bitch... You!" Ed flinched. "Get on your feet before the imposter gets here, what if he arrives ready to attack?"

Yeah, okay, that was fair. Ed used the shelf beside him to haul himself up with a grunt, and gingerly tested the leg's stance before he put his weight on it. Alastor squinted at him, but didn't comment.

All three of them spent the next few tense minutes watching the door, brought to a rather anticlimactic end when it slammed open. Dumbledore came in first, then the floating body of the imposter, and finally, Severus.

Dumbledore smiled at them serenely. "All is well."