Summary: It's Remus' final year at Hogwarts and he doesn't know what to expect with Professor Black as the new DADA teacher. Voldemort is gaining power, the wizarding world is in dispute, and Remus has no idea where he fits into all of it.

Warnings: Student/teacher relationship, slight age gap, non-graphic sex, violence, mild descriptions of gore, swearing, alcohol.

Author's note: Approximately 20 chapters total. Special thanks to TimeToWriteIsHistory for writing the summary for this story!

Story notes: This is a Remus/Sirius student/teacher AU set at Hogwarts, featuring Sirius as the teacher. 'The Marauders' don't really exist without Sirius as part of the group. James, Peter, and Remus are still close friends and they're still pranksters, but there's not quite the same sort of bond as what exists when Sirius is there.

"The Walls Between Us"
Part I: You and Me
Chapter One

He hadn't even been back at school for twenty minutes yet and he was already getting in trouble.

Remus had spent the summer telling himself that seventh year would be the time when he would finally say no to James Potter. No to bending the school rules to accommodate James' trouble-making. No to the foolish rebellions against teachers. No to tormenting Slytherins. And most importantly, no to the stupid waste-of-time pranks that James always dragged Remus along on.

But, as Remus was soon reminded, James Potter was a very difficult man to say no to. James would smile in that charmingly boyish way that would light up his whole face before he would strut off down the corridor, not even checking if Remus and Peter were following behind him. It was as if the universe revolved around James himself and there was no choice but to be sucked into his orbit. Remus would try to be angry, try to say no. But Peter would already be eagerly tagging along after James, and James would be rattling off vague details of his surprisingly clever plans. Did Remus really have any other choice than to follow after them?

So here they stood, just outside the doors of the Great Hall, Remus and Peter keeping watch while James positioned whatever sort of ridiculous charms he had come up with this time. Through the heavy doors of the Great Hall, they could hear that the Sorting Ceremony was over and Dumbledore's start of term speech had begun. Remus peered up the marble staircase, half-expecting to see Filch coming after them already.

Remus shot a look at James, hoping it would somehow convey his disapproval. But James wasn't even looking in his direction, and picking up on non-verbal cues was never one of James' strong points.

"Filch is going to kill you for this, you know, you're going to have detention until you graduate!" Remus hissed.

James was giggling madly. He glanced over his shoulder for a moment, a charming smile on his face. "You're a prefect, Remus, why don't you stop me?"

And why didn't Remus stop him?

Truly, Remus couldn't bring himself to do it. Remus really felt that he owed something to James, and to Peter as well. They had discovered his 'furry little problem' in third year. Remus had expected them to abandon him, to ridicule and even expose him, but they had been completely untroubled by it and they had kept Remus as their friend. Remus felt so thankful that he thought he would never be able to repay them. There was no way he could deny anything to either of them after that. So he made excuses for James' trouble making and let the rule-breaking slide, and he followed James on these stupid pranks.

And, though he would never admit it, there was another reason why Remus joined in on these pranks.

There was a certain thrill in breaking the rules. It was a decidedly un-prefect like thrill, but Remus couldn't deny that he truly enjoyed some of the ridiculous adventures that James came up with. The thought that they could be caught at any moment was an adrenaline rush like nothing else. Heart pounding, senses heightened - there was no other feeling quite like the feeling of breaking the rules.

James was grinning widely as he moved the last of the charms into place. "Finished!" he cried. He brushed off his hands and puffed out his chest, looking very pleased with himself as he surveyed the invisible charms.

Remus sighed, but he couldn't help but smile at James' delight. "Honestly, James, everyone is going to know it was you."

"Of course they will! I'm just giving those firsties a nice taste of what's coming to them this year. I'm transitioning them. Helping them to adjust to school life!"

Peter laughed. "A modern day saint."

James put on an innocent look that was entirely unsuited to his face. "Oh, you know I'm more modest than that." James stretched, looking between Remus and Peter before his face broke out in his typical boyish grin.

"There's no denying it, boys, this is going to an excellent year."

Remus just rolled his eyes.

By now, they could hear that Dumbledore's speech had ended and the noise of the students talking rose up loudly. It was still painfully conspicuous sneaking into the Great Hall, though a quick glance at the staff table didn't reveal that they had been noticed. James smiled sweetly at Filch.

They took their seats at the Gryffindor table and Remus noticed that it was unusually easy to find a seat. Arriving late to a feast usually meant that they would be sitting at opposite ends of the table in whichever chairs were left empty, but they had easily found three chairs together.

Remus glanced around the Hall, noticing that there were empty chairs at all the tables. Not many, but the hall was usually completely filled. There must have been students who didn't return to school. Remus couldn't say that he was surprised; with all the recent disappearances and deaths that had been reported in the Daily Prophet, it was no surprise that some parents must have thought that it was too dangerous to allow their children to return to school.

Recently the name of Voldemort had become known to the wizarding world. Voldemort was a dark wizard who had been gaining power and followers on the quest for purification of the wizarding race. It wasn't being called a war; The Ministry was quick to dismiss that possibility. But a series of mysterious and dark events surrounded Voldemort and his followers, and he was becoming so powerful that some people were even becoming afraid to say his name.

The disappearances and deaths had slowed over the summer and there was some hope that Voldemort had given up or disappeared, but Remus didn't think this was very likely. Remus' father, who worked at the Ministry, said that the Ministry was still struggling to deal with the threat of Voldemort.

"Did you miss me over the summer, Evans?" came the sudden sound of James' voice, bringing Remus back from his dark reflection. James was smiling charmingly at Lily, who was very focused on buttering a slice of bread and obviously trying to ignore James.

"Don't be ridiculous," Lily said coolly. "Summer was wonderful. Two whole months free from dealing with your pathetic advances."

"Oh Evans, you don't mean that. I'm sure you must have missed my good looks and charm."

With a small sound of disgust, Lily turned away and ignored James.

It was cute, almost, how these two toyed with each other. The way James was so obviously smitten but so obviously clueless about how to even have a conversation with Lily. And though Lily was always cruel to him, Remus couldn't help but wonder if there was something more to it. She did seem to pay quite a lot of attention to someone she supposedly detested.

"Hey, do you think that's the new Defence teacher?" Peter asked, pointing to the staff table.

Being that they had missed Dumbledore's speech, they had missed the start of term announcements and the introduction of new staff. From what Remus could see, there was only one new staff member.

The man was quite young compared to the other teachers, as he looked to be in his mid-twenties. He had black hair and a handsome face: pale eyes, high cheekbones, and a long elegant nose. He sat tall in his seat and seemed rather uninterested in whatever Slughorn was talking to him about.

"That pretty boy teaching Defence?" James laughed. "He wouldn't last five minutes against a werewolf!"

Remus jabbed his elbow into James' side. "Yes, it seems so," Remus hissed through his teeth. He had always been hyperaware of any mention of lycanthropy and he felt that there were times when James was just a little too casual about it.

But James only laughed it off, and he was soon distracted alternately by the feast and trying to get Lily's attention.

Oddly, Remus found his gaze drifting back to the new Defence professor. The man looked strangely familiar, but Remus couldn't place where he had seen that face before.

When the feast was over, Dumbledore spoke a bit more and then bid the students goodnight. Remus joined the other Gryffindor prefects in gathering up the first-years and getting them ready to be lead to the Tower. He was leaving the Great Hall with a group of students when it happened.

Custard.

Custard pouring down the walls, spraying out of doorways, bubbling up from the stone floor. So this was what James had been doing with those charms. Some students were slipping in the mess, some were screaming, and James was standing in the middle of it all, laughing like a maniac.

Remus struggled desperately to get the group of screaming first-years to the stairs. A custard fight was beginning to break out amongst the fourth-years when Filch finally appeared, waist-deep in tapioca and wading towards to the still laughing James.

James didn't go without a fight. Remus could only watch as a great wave of custard swept over Filch and a group of students. James was still laughing manically, looking like a crazed emperor watching his kingdom crumble before him.

Seventh year was shaping up well already.

Remus had to admit that the custard flood had been an impressive bit of magic. He couldn't even imagine how James had managed to bend Gamp's Law. Even McGonagall seemed vaguely impressed, though she had still given James detention and made him clean up the mess without magic.

And, even though he had already broken his vow to say no to James, Remus couldn't deny that the chaos of the custard flood had been quite funny. James certainly thought so as well. Despite that James had been scrubbing custard out of the cracks in the floor until close to midnight and had detentions for a week, he was still grinning happily at the breakfast table the next morning.

"We're off to a good start already, boys!" he said loudly around a mouthful of eggs, "That was a disaster in the best possible way. What do you suppose we should do next?"

Lily shot a disapproving glare at James. "I don't know, Potter, how about you grow up and stop making everyone else's lives miserable?" she said coldly.

Even Lily's cold words weren't enough to deter James' spirit. He blew her a kiss and heartily dug into his breakfast. He was nearly skipping as they made their way to Charms.

But as Flitwick started going over the course syllabus, Remus could practically see James deflating. Listening to Flitwick outline all the assignments, essays, and exams that would be required this year was like watching an increasing weight upon James' shoulders grow heavier and heavier. By the time class was over and they were making their way to the Defence classroom, James was slouched over and miserable.

"Look at all this homework already! And that was only the first class. I thought this year was going to be great, but between this and Quidditch I'm not going to have time for anything."

Remus frowned. The thought that James was actually worried about school was almost a bit frightening. "What did you expect? We have to write our NEWTs this year. You can't just skive off classes and hope to pass like you always do."

James smiled, seeming to shake off a bit of his melancholy as they entered the Defence classroom. "Oh Remus, you know me so well. That is what I always do. And I always come out at the top off the class, don't I?"

Peter gazed up at James admiringly, but Remus could only roll his eyes. "You and your ego."

Remus was joking, of course, and perhaps only a bit jealous of James' natural genius. But really Remus didn't mind having to study to get good grades. He enjoyed school and he was looking forward to the first Defence class.

James led them to a table near the back of the room and they began unpacking their books. The new professor hadn't yet arrived in the classroom and students were chatting amongst themselves.

Ah, the joy of a new school year! No matter how James and Peter teased him for it, the beginning of a new school year was pure delight for Remus. Books waiting to be read, essays waiting to be written, new spells and charms to be learned. Remus was nearly dizzy with the smell of a fresh roll of parchment.

"Wonder how long this one is going to last?" Peter mused out loud, effectively knocking Remus out of his parchment-induced trance.

In their seven years at school, they had had seven different Defence teachers. The rumour that the position was cursed had been around since before they had even started at Hogwarts. The staff were quick to dismiss the rumour, saying that this fabled 'curse' was only a product of the overactive imaginations of school children. McGonagall had even once suggested that James was driving the teachers away with his endless tormenting. It had been the closest thing to a joke they had ever heard from her, but there was definitely some truth in the sentiment. Even now James' mischievous smirk had reappeared with the prospect of a fresh new teacher to prank.

"Let's show this pretty boy how things are done around here!"

James snuck up to the chalkboard with all the subtly of a bull in a china shop. Peter was laughing, but Remus just sighed and turned to his textbook. The deliberately cruel pranks that James pulled had never appealed to him.

James had that boyish grin on his face as he hurried back towards their table. He had barely made it back to his seat when the professor sauntered through the door, kicking it shut behind himself.

"Alright, everyone settled down and shut up. Let's just get this over with. Don't think for a minute that I'm here because I want to be, but you can thank your Headmaster for putting me here."

The atmosphere had instantly darkened and students were shifting around uncomfortably. Remus stared at the professor in disbelief. There had always been a few grumpy professors, but none had ever made a commotion like this in front of the class. It seemed almost childish.

The professor grinned, though there was no humour in it. "But I guess if I'm teaching this subject then I'll be out of here before the year is over anyway."

Someone near the front of the classroom actually gasped at that. No teacher had ever acknowledged the supposed curse on the Defence Against the Dark Arts position.

The professor seemed unconcerned with the uneasiness he was causing.

"I'm Professor Black, as I'm sure you all heard at the feast. Being that you're seventh-years now, the curriculum focuses on..."

Black continued on, but Remus didn't hear any of it. He could feel the hairs on the back of his neck standing on end as he realized why he thought this man looked familiar.

It had been over ten years ago and Remus could still clearly picture it in his mind. It was a very special day that Remus was allowed to go visit his father's office at the Ministry. Brimming with excitement, he had stood holding his father's hand as they waited for the elevator that would take them to his father's office. There was a 'ping' as the elevator stopped at their floor, and as the doors opened a man in dark elegant robes swept out with such ferocity that he knocked Remus' father to the ground.

The man sneered down at the Lupin men with a look of pure disgust on his face. He wasn't unusually tall, but Remus felt like an ant looking up at a giant.

"Mudbloods," the man had said to them in cold, level voice, "only give rise to more Mudbloods."

The man brushed off his robes as if bumping into Remus' father had dirtied them and then swept off down the hallway without another word.

Remus' father jumped to his feet, wand clutched in his hand. "Don't talk like that in front of my son!" he shouted after the man, but the man didn't look back.

When Remus reached for his father's hand again, his father was shaking with anger. It was nearly an hour before he finally calmed down to speak to Remus. Remus' father then explained that the man had been Orion Black, a terrible man who looked down at anyone who didn't come from the old pure-blood families.

The encounter outside the elevator had been so frightening to Remus that he had never forgotten it. That face... Remus could still see Orion's disgusted face clearly in his mind. Pale eyes peering down a long straight nose, black hair, high cheekbones... There was no denying that this new professor was part of the Black family. He looked just like Orion had, and if he knew that Remus was a werewolf, then that same disgusted look would be on his face soon enough.

The Blacks, the Malfoys, the LeStranges; Remus had always made sure to keep his distance from anyone from the old pure-blood families. It was bad enough that he was a half-blood, but if they found out that he was a werewolf... Remus knew there would be no hesitation in attacking or even killing him.

And now, Black knew. He had to know. All the staff knew, didn't they?

Maybe, maybe Dumbledore hadn't told Black. Maybe he had foreseen that Black might attack Remus if given the chance so he had kept Remus' lycanthropy secret. Dumbledore was a smart man, after all, and he wouldn't put his students in danger like that.

Black was still going over the syllabus, now discussing the dark creatures they would be learning about. Of course. Turn the rest of the students against Remus as well. Remus could imagine it: perhaps they'd go over the Homomorphus charm, and look!, here's the perfect dark creature to try it on.

Black was reaching for the chalk. "... And we'll also be learning defensive spells against-"

There was a loud explosion and Black was left standing at the front of the classroom with his face covered in soot and a rubber chicken in his hand.

The class gasped in shock. A few students laughed but tried to cover it up. But it would have been painfully obvious who had set the prank even if James wasn't the only person in the room laughing ridiculously loud.

As Black's gaze turned towards their table, Remus instinctively tensed and sunk lower in his chair.

"Fake chalk? You put that here?"

James was still laughing as he nodded. James was never one to pass up taking credit for his pranks.

And then, Black laughed.

"You altered the fake wand charm to work on any object? Brilliant!"

James went silent in shock and Black grinned at their table. Remus tried to sink even lower in his chair.

"I've heard about you already. I'm going to take a wild guess and say you're James Potter. And that would make you two Peter Pettigrew and," -there was slight but distinct pause, "Remus Lupin."

Remus avoided eye contact, but he could still feel Black's gaze lingering on his face.

Black continued going over the course outline, but Remus didn't hear any of it. His hands were shaking and his heart was pounding like it would burst out of his chest.

Black knew. He definitely knew.

Remus tried to regain his composure but he felt like he could hardly breathe. Calm down, he told himself. A teacher wouldn't attack a student in the middle of class. He couldn't. Even outside of class, the school rules would forbid Black from doing anything to Remus.

But with that outburst at the beginning of class, Black didn't seem like one to follow the rules.

Remus focused on trying to disappear into his chair as class continued on. James was abnormally well-behaved and eager to answer questions throughout the rest of the lesson, which meant that Black was looking at their table quite often. Remus fixed his eyes firmly on the words in his textbook but he still felt that Black's gaze would linger in Remus' direction.

Despite the fuss Black had made at the beginning of the class, Black seemed like he would be a good teacher. Even Remus was impressed by Black's lecture and his ambition for the class. Black clearly had experience facing the Dark Arts (or, being that he was a Black, performing the Dark Arts), and after class students were already excitedly discussing the spells they would learn this year. A group of girls were also busy discussing how handsome their new professor was.

James' good mood was restored and he talked about Black as they made their way to the Great Hall for lunch. "Did you hear what he said? 'Brilliant'. 'Brilliant'! Imagine if McGonagall said something I did was 'brilliant'! I'm telling you, this is going to be an excellent year."

"Do you think he's part of the Black family? The pure-bloods?" Peter asked as they took their seats at the Gryffindor table. Peter glanced over at the Slytherin table, likely thinking of the Black sisters who had graduated a few years back.

Remus knew that there was no denying that face. "He is. He looks just like them."

"It seems strange that someone from that family would be teaching Defence Against the Dark Arts. I thought the Blacks were all about Dark Magic."

"Who cares?" James said, waving his arm dismissively. "He's great! He though that my fake chalk was brilliant."

"Sounds like someone has a crush," Peter said teasingly.

"What? No! My heart belongs to one person, and one person alone." James cast a longing look over at Lily, who was sitting near the other end of the table. Lily wasn't facing James but she seemed to sense his gaze, and a shiver of disgust ran through her body.

"It's just - Professor Black and I, we're like... we're like kindred spirits! What did I say, boys? An excellent year!"