At fifteen years old, Severus Snape knew rather more about most things than he should. He knew about the hidden rooms of Hogwarts that held centuries of unguarded secrets, and the dark places below the Slytherin common room. He knew about places otherwise lost behind passwords and passageways, and how to bribe and trick his way through both. He knew what it was like to be hated because of the green badge on his cloak, and knew how to hate the splash of red that marked the likes of James Potter. He knew what it was like to love your best friend before he knew what love was. He knew, above all, what it was like to be lonely.

Rather more pragmatically, what he knew at this precise moment was that he was all of a second away from being either thrown bodily out of the nearest window or cursed into a smoking black smudge on the castle floor.

And rather more crucially than that, he knew it was James Potter's fault. If he survived this, Potter wasn't going to.

The classroom was dead silent. Severus didn't move, wand stretched out in front of him and arm locked in place by sheer horror and no small amount of self-preservation. It was still pointed incriminatingly at the dark haired substitute professor; the one currently suspended upside down by his ankle and regarding him with icy calm. Severus had the sudden urge to drop his wand and run, an urge quickly quelled by an animalistic knowledge that he should under no circumstances turn his back on this man, or go into the rest of this confrontation unarmed.

His classmates, Syltherins and Gryffindors both, edged away from his, stools scraping quietly on the stone floor. All, Severus noted with disgust, but the ones containing Potter and Black, who didn't even have that much sense, and were simply looking, open mouthed, between him and the teacher.

Professor Crowley looked at him for a moment, face impassive.

"I would advise you at this point to close your mouth and lower your wand."

Severus closed his mouth with an audible snap. Blushing as he took several steps backward, he only barely twitched his wand downwards.

He must have blinked because suddenly Crowley was standing, the right way up, on the stone floor, snakeskin shoes making a smart click that echoed quietly in the otherwise silent corridor.

Teacher and class eyed each other. If a casual passerby had felt the need to look directly into the eyes of and of the assembled fifteen year olds, the echo of the last student to upset Crowley could be seen flashing across them- with the soundtrack of terrified screams and exploding cars, helpfully supplied as they were by the juvenile subconscious. Alison Watchwater had had to be taken to the Hospital Wing to calm down, and later moved to St Mungo's for therapy.

"I'm so sorry," Severus blurted out. "I'm so sorry, Professor, I thought that—"

He broke off, for two reasons. The reason he'd hexed Crowley was that he'd thought that the teacher had been Potter. Given that the latter had spent the last three-quarters of an hour enchanting parchment to skid away from him a second after he'd started writing on it, leaving him with two feet of black ink scratching over his Defence notes, Severus felt he was justified in wanting to see the boy strung up by his ankles. Preferably with Black sharing the ceiling too if he could get the second hex in fast enough, and he was capable of dealing with the resulting fall out.

But it wasn't in Severus to snitch, for whatever reason; he preferred sneaking vengeance to a teacher's short-lived interference. Nor was it, for that matter, in him to whine to a teacher, and expect them to do something about it. He believed in fighting his own battles. Secondly, Severus didn't think that this justification was going to help him. Crowley didn't seem like the sort of teacher who would bother attempting to exert influence on classroom warfare, and, more importantly, didn't seem like the kind of person who would let direct assault slide for any reason. The best he could do, Severus thought with resignation, was try not to cry like Michael Cottrell had done last lesson.

When he didn't continue, Crowley let out a threatening hiss of air in a sinister sigh. "I see."

Severus said nothing, eyes flicking about the room as he struggled to find something to look at. He wasn't going to look at Crowley—there was something about the teacher's eyes that touched a primate part of him and made him want to curl up into a tiny ball and die—and he wasn't going to look at any of the other students, because they would think he was scared. He settled on Crowley's mouth, set as it was in a tight line, and tried to remember to breathe.

"I think," Crowley said at length, "That here our lesson concludes. If you'll all pack up your things, except for you," he didn't need to clarify any further than that, not even bothering to look at Severus as he glared around the rest of the class, "And you, Potter."

"Me, sir?" Potter yelped, managing to sound as if he genuinely believed he was being unfairly accused of something.

Crowley gave him a pointed look, and Potter went uncharacteristically silent, innocent expression crumpling up in resignation. There was a sudden scramble of movement as the class rushed to pack their bags and scurry out of the room. Sirius grinned at James as he passed and slapped his shoulder, barely faltering when he caught Crowley's gaze, but hurrying out the room. Severus tried to catch the eyes of Avery and Mulciber, but the two boys determinedly avoided his look and left the classroom.

"Potter, you will wait outside," Crowley said calmly, waving his wand at the books and papers on his desk as the student complied. The items picked themselves up and stowed themselves into the dark green snakeskin bag on the floor.

"What spell was it?" he asked without preamble as the door to the classroom swung shut.

"What? The spell?"

"Yes, you didn't say it aloud, did you?"

"Um, no, sir. It's called Levicorpus," Severus said uncertainly when the teacher's eyes continued to stare unbendingly into his.

"That's a new one." It was a statement, not a question. "Where did you learn that?"

"I… A book, sir," Severus replied.

"If you're going to try to lie to me, you will need to get a lot better very quickly," Crowley said sharply. There was a brief moment in which the professor's lips pulled back to reveal impossibly white, sharp teeth, before the appearance dropped and Crowley's composed expression was back in place.

Severus flinched. "I didn't learn it anywhere, sir."

"Right. So, you created it?"

"Yes, sir."

"That's impressive, you know," the professor said, though it didn't sound quite like a compliment. Crowley's eyes bored into his, and Snape shifted uncomfortably as he fought to look anywhere else.

"Thank you," offered Severus cautiously.

"Mm. And who did you think you were firing this spell at?"

Severus said nothing for a moment. "It was more a reflex. Sir."

"You can drop the 'sir'," Crowley said, eyebrows lifting. "That was a slightly better lie. But you do know that your ongoing war with James Potter and his entourage isn't a secret?"

Gaze shifting abruptly, Severus looked at him straight on and ignored the agitated curl in his stomach as he met Crowley's eyes.

"I see." Crowley looked satisfied the provoked response. "There's a betting pool with the teachers concerning yourself and Lily Evans as well, if that's any interest to you."

Severus blinked and looked away, back to his shoes, completely off-balance. Hidden by his sleeves, he unclenched his hands carefully. He'd fallen out with Lily three days ago, and she hadn't spoken to him since. They'd not argued before, so he didn't have anything to compare it to, and he'd never had any other friends to fight with. With no precedent, and no idea how to make the situation better, Severus had been reduced to simply hoping that she'd forgive him, and start talking to him again.

Trying quickly to think of something else just in case the professor could read his mind, which didn't seem unlikely, Severus blurted out,

"You teach Herbology, don't you?"

"Currently," Crowley allowed, "Professor Beery left to follow his dramatic calling*, and his replacement will not be here for another month."

"I remember in my first year," said Severus after a moment's hesitation. "You covered Transfiguration."

"My skills extend over many fields," replied Crowley smugly. He leant back against the desk, stance relaxing from the commanding pose he had been teaching in.

"But there was another teacher with you?" Severus prompted, keen to distract Crowley from his surely impending punishment. "One of the other students, she said that you always came together?"

The matter of Crowley and Aziraphale was of distinct curiosity among the student population. Students with older siblings and parents who had gone to Hogwarts reported that they had been covering for absent teachers for at least two decades, but in all that time did not appear to have aged. This wasn't, in itself, too unusual; magic did have strange effects on aging in some wizards, inadvertently or otherwise. What was unusual was that the two of them came together when only one professor was needed, and, more pressingly in Severus' opinion, that as soon as they'd gone, nobody seemed to remember that they had ever been until they were back again.

As long as he wasn't getting detention for accidently jinxing the professor with a spell that hadn't been formally tested, Severus thought he could try and get away with a little snooping. The fact that Crowley hadn't regained control of the conversation straight away was in his favour.

Some of Severus' confidence evaporated as something in Crowley's demeanour stiffened. "He's busy," Crowley said, tone perfectly balanced between dismissive and foreboding.

"Okay," Severus very nearly squeaked, except he was fifteen years old and a Slytherin, so that sort of thing was beneath him. In the depths of his robes, Severus clutched his wand.

For a few seconds, neither of them said anything. Then Crowley seemed to reach a decision.

"Do you know why the Headmaster is not at Hogwarts?"

Severus blinked, but nodded cautiously. "He's fighting. In the war, the war between the Ministry and You-Know-Who."

"The Ministry," Crowley repeated with a derisive snort. "It's a war between Voldemort and Dumbledore, and the Order of the Phoenix." He paused, presumably waiting for Severus to say something, which he didn't, despite the fact he had never heard of 'the Order of the Phoenix'. "I'm here as a favour to him.

"He asked Aziraphale here too, but he wouldn't leave London. That's the main battleground, you know, and no wizard with sense is living there anymore, but obviously no-one can move all the Muggles."

Stopping again, Crowley seemed to consider his next few words carefully. "Do you know why I'm telling you this?"

"No," Severus said bluntly.

Crowley smiled. "It's going to be your war one day, kid. Yours more than most. Just so you know." The teacher hesitated, minutely, a flash of internal conflict in his odd honey-coloured eyes.

"There are more than two sides in a war; as many sides as there are combatants, and that includes foot soldiers. When… Just remember that. More than two sides. Just because other people might think you're on one, it doesn't meant you can't have your own agenda. Thinking life is as clear cut as good and evil is a Gryffindor concept."

Halting abruptly, Crowley gave him a scrutinising look. Uncomprehending, Severus met his gaze blankly.

"Alright, sir," Severus ventured after the silence had stretched out.

The professor sighed, and shook his head. "It doesn't matter." He straightened, almost imperceptibly, and cast his eyes briefly upwards.

"Send Potter in, will you?" he ordered, even if it was phrased like a request, gesturing to the door. Severus tried not to bolt, and didn't mention the lack of punishment.

"I'll expect you in my office at nine o'clock this evening," Crowley said from behind him. His grin was audible, and Severus reconsidered the possibility that the man could read minds.

The snort that may possibly have been an answer to that wayward thought was not encouraging, and Severus beat a hasty retreat. Potter was waiting outside the door, and Severus took great care to hit him with it as he went past.

"Snivellus," Potter muttered, crashing into him as they both tried to walk through the same space at once.

"Potter," Crowley said sharply. "In."

The boy paled slightly and disappeared into the room. Severus was half way down the corridor when a thought occurred, and he stopped, looked around and walked quietly back.

That probably wasn't what Dumbledore had had in mind when he'd asked Crowley to talk to Snape. The old wizard had been watching Severus for a while, the same way he'd been watching James and Lily, and a number of the other children in their year. These were the children, after all, that had parents who were Death Eaters and Order members. They warranted the attention.

Dumbledore thought Severus had the potential for a spy. His guerrilla tactics against the bullying of James Potter during their first two years of school together were noteworthy in their success, and the boy's mother was also cause for interest; a blood purist who converted and married a Muggle without a drop of Wizarding blood in his body. Dumbledore didn't see a swift conclusion to the war, and such measures of observation were prudent, he said.

Crowley, for his two pence, wasn't sure why Dumbledore thought he was more suited to running a school than the Ministry, or at least the Department of Magical Law Enforcement. There was quite a bit about Dumbledore Crowley wasn't sure about; but Aziraphale liked him.

Aziraphale was on his mind rather more than Crowley wanted, these days. He wondered what his counterpart would have done, if Dumbledore had given him the same task—probably a better job of it. Then again, it was only Aziraphale's superiors that were keen on the whole 'greater good' thing; it was getting harder to predict the behaviour of the angel himself. Crowley was personally more for self-preservation, but again that was probably more of a snake thing than a true reflection of Hell's values. The principles of a 'greater good' held some attraction to them too.

He dismissed James without much thought, with vague threats of a surprise detention lingering over him to keep the teenager on his toes. The kid had barely gotten out of the door before he let out a high-pitched scream of surprise. Crowley stuck his head out of the door, to see James hanging upside down in mid air, screaming expletives down the seemingly empty corridor. Unseen, Crowley retreated back into the classroom opted to leave Potter to it.

* This was said with a malicious sort of amusement; Snape recalled briefly the fire that had broken out at Beery's final production at the school. The Great Hall had been partially demolished when two conflicting angles of a supposed love triangle had caused when they had started duelling in the second act. Nobody had stopped them for almost a quarter of an hour because they were convinced it was part of the show.