A/N: Thank you SO MUCH to everyone who reviewed/favourited the last chapter; you totally made my week. In answer to one particular review: in line with canon, the 'Willow Incident' will take place in fifth year, before the events of Snape's Worst Memory.

Chapter Five: The Art of Diplomacy

27th March 1976

Severus thought it would get better, but it didn't. It got worse.

He'd been under the impression that he hadn't seen much of Lily recently, but suddenly she seemed to be everywhere, with her beautiful laugh and her radiant smile. And Potter was never far behind – performing some idiotic joke with Black, offering to carry her books, messing up his stupid hair to give a windswept look Severus could never hope to achieve. He'd actually tried it, on Friday night, but his hair had remained stubbornly limp and lank, before Severus had tried to charm it and had ended up looking like he'd stuck his fingers into a Muggle plug socket. He hadn't quite managed to fix it before his dorm mates had come in. Avery had nearly wet himself laughing.

It was just so unfair. Potter was good at everything and everyone, with the exception, perhaps, of some of the Slytherins, couldn't get enough of him. Severus had never considered himself so pathetic as to be jealous of James Potter, but it dawned on him, as he stood in front of the bathroom mirror comparing his skinny white chest with what he imagined to be Potter's Quidditch-toned body, that jealous was precisely what he was. The thought had made him want to yell and smash up the whole dorm, but instead he had simply leaned, scowling and shivering, against the mirror, wondering what had changed.

He knew. Of course he knew. It had never mattered how clever or likeable Potter was, because Lily had never liked him. But however much Severus had hoped that that first day had been a fluke and that Lily would snap out of it, he had seen her slightly shy smile and the way her eyes sparkled as she spoke to Potter and he knew he'd been wrong. What a bloody fool he'd been, to think that Lily wouldn't be blinded by Potter's charm like every other damned person in the school!

It had only been a few days but it seemed like an eternity, he thought as he sat in the dungeons on Saturday night, ignoring those around him and brooding on the fact that today had been Potter's birthday. As he sat listening to another pointless lecture Severus could have recited backwards in his sleep, Lily was up in the Gryffindor Common Room enjoying the festivities her House were no doubt holding for their star Chaser. She'd even given Potter a present. Severus knew – in fact, the whole stupid school knew – because Potter had made a fool of himself thanking Lily in such an exaggerated fashion that even his friends had mocked him. Lily had blushed a deep, dark red that made Severus's blood boil. All for a bloody box of chocolates.

It was enough to make anyone sick.

And it seemed to be all he could think about: it was occupying all his thoughts during the day and keeping him awake at night, creeping into his dreams even when he managed to fall asleep. If only, Severus thought resentfully as he glanced around the small room the Slytherins used for these lectures, Nott had allowed him to give this lecture: that would have distracted him. He could have given the lecture: all the seventh years' materials were derived from a collection of books Severus had read cover to cover twice and more besides. But he had offered to give a lecture once before and Nott had looked at him with such pitying contempt that Severus's cheeks still burned angrily thinking about it. He had resolved never to offer again, and so he was stuck obsessing over Lily and James Potter while Nott droned on at the front.

At least everyone else seemed to be oblivious to the fact Severus's thoughts were on anything but the development of Dark curses. In fact, several others looked miles away – and not, Severus thought scathingly, because they could afford to, as he could. Jugson – who, frankly, had trouble stringing two written sentences together – actually had his eyes closed, while several of the third years, the youngest present, looked like they were desperately trying to stay focused on concepts that were well beyond them.

Burke, on the other hand, looked sharp and alert, as did Mulciber – a sure occurrence whenever anything particularly dark was being discussed – but both of them were watching Nott intently, ignoring their distracted dorm mate behind them. Avery, somewhat surprisingly, was actually making notes – no doubt because he saw this as an opportunity, finally, to match Severus's skill in creating hexes and curses.

Fine chance of that, Severus thought. He had been developing such spells for years: it took imagination, patience and a deep appreciation for how Dark Magic worked in order to achieve any results. Avery, born with a silver spoon in his mouth, could not wait for anything: he expected everything to appear at his fingertips and became instantly restless if he had to put in even a small amount of effort.

Satisfied that the people around him were well distracted from Severus in some way or another, Severus sank back into the back of his seat, his thoughts returning to Lily. He wondered what she was doing at that moment. He had never, of course, been to a Gryffindor party, but he had heard enough from Lily to provide enough furnishings for his imagination: probably she was perched on the edge of a deep red settee, sipping Butterbeer and laughing with her friends – or perhaps at one of Potter's stupid jokes – while he, Severus, was slouched on a hard chair in the third of these pointless meetings this week…

"-And it's about time someone did something about Potter fawning over that Mudblood; it's a disgrace."

He had not been paying attention. But at Potter's name, Severus suddenly sat bolt upright and had said, "What?" before he could stop himself. A few people around him tittered: the animosity between Severus and Potter was well known. Severus ignored them, his heart hammering. He had heard Potter's name in conjunction with 'Mudblood', and there was only one person of that description that they could mean…

"You must have noticed," said Rabastan Lestrange a little impatiently. Although Nott – considered by most to be the most superior in blood terms of the seventh years – gave the appearance of being in charge of these gatherings, it was really Lestrange who controlled them. Also a seventh year pureblood, he was sharper than his older brother had ever been, and no less cruel. He was not someone to get on the wrong side of. He eyed Severus coldly now, his blue eyes hard. "Potter's been all over that Evans filth."

"Careful, that's Snape's Mudblood you're talking about," came Burke's sly voice from in front of Severus. Severus felt like whipping out his wand and hexing the back of Burke's head. But perhaps he should have expected it: Burke never missed an opportunity to get in a dig at anyone.

"You're not still going around with that muck, are you, Snape?" Wilkes, a sixth year with far too much arrogance for Severus's liking, looked amused, though the dangerous edge to his voice made it sound more like a threat than a question.

Severus ignored him. "The fifth years discussed this the other day," he said. "We agreed nothing could be done under Dumbledore's nose. Potter's father's a school governor, for a start." It left an unpleasant taste in his mouth to say it – he would have liked nothing better than to have set the whole of Slytherin on Potter's smirking face – but he knew he could not behave too protectively of Lily alone, lest he raised his fellow House-mates' suspicions.

"Well, obviously, it's not Potter we'd be teaching the lesson to," Lestrange drawled. Severus's blood turned to ice. Somehow it had never occurred to him that they would blame Lily rather than Potter. But of course they would – because Potter's misdemeanour was a mere transgression, whereas Lily's, in trying to attract a pureblood, as they saw it, was tantamount to treason. Severus hated Lestrange at that moment, with his sneer and blood that made him think he was entitled to do as he pleased. But he was aware, somewhere deep inside him, that he hated Potter even more: he was the one going after Lily; he was the one making her a target, with no thought for anyone but himself. The thought made Severus want to storm up to Gryffindor Tower and blast James Potter into pieces.

"We should make an example of Evans," Mulciber spat. "Send a message that Mudbloods can't get away with this."

Severus said nothing – what could he say, without making it look like he was protecting Lily? Luckily, Burke swooped in instead – though he liked to watch others squirm, and was no doubt enjoying Severus's discomfort, he was never stupid.

"Let's be serious," he said. "It's a nice idea but, like Snape said, Dumbledore would never tolerate it."

"Who cares about that Muggle-loving idiot?" asked Avery.

"No one here," Burke returned sharply, "but not all of us have dads on the governing board, Avery."

"Enough." The bickering, which had started to resonate in low murmurs across the small room, ceased immediately at Lestrange's commanding tone. His narrow eyes surveyed the room, and Severus watched him worriedly, trying to keep his face blank while his heart hammered so hard it threatened to burst out of his ribcage. The seventh years would call the shots: if they wanted to make Lily pay, the rest of them would be expected to fall into line; if they decided to leave her alone, Lily would be safe.

"We wait," Lestrange announced eventually. "Potter's all over her but he's not actually done anything about it. Any message we sent now might not be clear enough; he isn't quite a blood traitor yet. No, we wait until the opportune moment."

Rabastan Lestrange had a frustrating habit of using vague phrases without defining them and typically he did not now move to explain when the opportune moment might be. Perhaps, most likely, he did not know himself. Certainly it seemed that he was waiting for something to happen – for Potter to make some move that would make his allegiance obvious. And though Lestrange would not be too afraid of expulsion, being so well connected, he would no doubt want to ensure, if possible, that the teachers would not find out who the culprits were.

Right, Severus thought, his heart slowing down somewhat as Nott dismissed them all and chairs started to scrape back and murmurings rose around him. So she's safe for the moment. But it would not take much, he realised – Lestrange must have meant that he was waiting for Potter to actually go out with Lily, or to be caught kissing her, or something… The thought made Severus's stomach churn: surely Lily wouldn't allow it…! But he couldn't be sure – not the way she had been behaving. And if she did go out with him, he would be clinging onto the thin hope that Lestrange simply did not want the aggravation of being caught cursing Lily.

"Coming, Snape?" Rosier asked beside him.

Severus nodded mutely. He had to talk to her, he realised: he had to make her see sense. She couldn't go out with Potter.

Severus's abilities in the Dark Arts might outstrip the knowledge of the idiots around him by miles, but Lestrange alone knew enough to cause Lily some very serious damage. Combine him with Nott or Mulciber, and Severus did not like to think of the consequences.

Curse James Potter and his self-centred arrogance, Severus thought furiously as he followed his House mates out of the concealed entrance to the room. He'd make James Potter pay for this. And if Lily got hurt because of him… Severus's hand twitched towards his pocket before he gave himself a mental shake.

Lily first. Then he'd deal with James Potter and his bloody hair.

28th March 1976

By all accounts, James should have been feeling pretty pleased with himself. The plan was going pretty well, even by Sirius's critical count: he'd carried Lily's bag to lessons three times in three days; he'd partnered her in Charms and impressed her with his knowledge of Colour-Changing Charms (derived entirely from a rather brilliant prank they'd played in second year); and the day before she'd given him a birthday present. She'd danced with him at his party. Not even Peter pointing out that the chocolates weren't even all that good should have been able to bring James down from his high.

And yet on Sunday morning he woke up feeling distinctly off. Initially he put it down to Sirius pouring too generous a helping of Firewhiskey into his punch the night before, but after a long lie-in and a cooked breakfast that was usually enough to throw off anything Sirius could throw at him, James came to the conclusion that, physically, he was fine. The feeling of something not quite sitting right was coming – and he grimaced even as he thought it – from him.

He didn't voice this to his friends, of course – Sirius would have killed himself laughing – but he took himself off for most of the day alone. He told himself it was to test the new broom his parents had sent him for his birthday. Although he wouldn't deny taking some delight in the easy way it twisted and turned at the lightest touch, he wasn't quite as pleased as he should have been, as he would ordinarily be. Nor, in spite of the fact he spent some three hours or so flying, did he feel any better at the end of it, the way he always did after flying. Instead, he left the Quidditch pitch with a heavier weight on his shoulders than ever, a grim feeling settled over him that he knew what he had to do.

And so ten o'clock on Sunday evening James found himself sat on the window ledge of the Astronomy Tower, facing in rather than out, so that his legs dangled into the room, as he waited for the wisest person he knew to find him.

Sirius would have said it was a bad idea, James thought as he kicked his heels against the wall, but then Sirius thought anything that didn't involve him was an inherently bad move. It did feel a bit odd, to have given Sirius the slip so he could come here. He'd never done it before.

Just as he was contemplating the idea that perhaps he should just go back to Sirius and forget the whole thing, however, there were footsteps on the stairs and, suddenly, a silhouette appeared at the top of the stairs. He did not immediately see James as he walked over to examine the cupboard, but James cleared his throat and the figure whipped around, his wand almost blinding James before James could open his mouth to speak.

"Merlin, Prongs," said Remus, the wand lighting up his pale face, "don't ever do that to me again."

"Bit jumpy for a snooping Prefect, aren't you?" James shielded his eyes against Remus's wand. Remus rolled his eyes and lowered it.

"There's never anyone here," he said. "And if there were, they wouldn't usually clear their throats."

"No need to be jumpy, then, is there?" James asked. Remus merely raised one eyebrow, and James's grin dropped. They both knew that this was odd, James being here alone. It wasn't as though he hadn't waylaid Remus on his Prefect duties before, but he was never by himself, and certainly never lying in wait like this.

"To what do I owe this pleasure, Prongs?" Remus asked eventually.

"To what do you owe this pleasure?" James mimicked in an overly proper voice. Remus fixed him with a hard stare. James winced and kicked his heels against the wall again.

"It's Lily," he said. It struck him that if he'd been talking to Sirius – not that he would've spoken to Sirius, not about this – he would have called her Evans.

Remus's expression turned from exasperated to amused in seconds. "What about her?"

"I…er…" Merlin, why was it this hard to say? He was afraid of looking like an idiot – that was it. It just wasn't cool to go about worrying about what was right and proper and all that rubbish. "It's nothing," he muttered. "I should probably go before you dock points – "

"You're worried she likes you for the wrong reasons," Remus interrupted, and it was so completely bang on the mark that James had to stare.

"How do you do that?" he asked finally.

Remus's lips twitched, as if at some internal joke to which James was not privy. James waited a moment, but the urge was too great – the words came tumbling out before he had time to second-guess them again.

"It's obviously great she seems to like me, but I'm on my best sodding behaviour – and it's not even for her; it's for you, and to wind Snape up; and that all seems…wrong somehow? Like we're...I dunno, using her or something." His words had started quickly and coherently, but he trailed off uncertainly at the end as he voiced his worst fear: that if he ever persuaded Lily Evans to go out with him, he didn't want it to be because he had ulterior motives. The uncertainty, deep in the pit of his stomach, only grew as Remus studied him silently. Perhaps he should have listened to the Sirius-voice in his head, he thought: Remus was not the right person to come to; Remus had been against this plan from the start…

"You really like her, don't you?" asked Remus at last.

Defensiveness rose in James – he was rapidly turning into the biggest loser in the school. "Don't be daft," he said. "She's just a bird." But he found himself fervently hoping that he had not already kept Remus so long that Lily came to find him – that she had not overheard him.

Remus was studying him again, his pale green eyes glinting in the dim light. This had definitely been a stupid idea. James slid off the windowsill and jumped down onto the ground.

"Well, thanks for the chat, Moony," he said briskly, as if they'd been discussing the Quidditch League. He messed up his hair with one hand – just in case he ran into Lily. "I'll see you back in the Common Room."

He had taken two long strides towards the stone steps when Remus spoke again.

"Put it another way, Prongs," said his friend. "Maybe it's not Lily you're using."

"Snivellus, you mean?" James whipped around, but the suggestion died on his lips, because the look on Remus's face told him exactly whom Remus thought he was using, and it wasn't Snape. James stared at him, open-mouthed. "Moony – you can't think – I wouldn't – " The way Remus did not look away somehow made it worse. "We're just trying to get Snape off your back," he said.

But doubt was gnawing at him – it had been Sirius's suggestion, but had he only agreed to this plan because it meant he would get Lily? Bloody hell. He had spent the whole day questioning if he was using Lily as some sort of pawn when he should have been wondering if it was wrong to go against what Remus wanted when it was Remus's secret. It was the worst kind of plan, James realised in a rush – the sort of plan in which no one was happy and everyone had the potential to get hurt.

"We'll give up if you want," he said finally, though it pained him to say it, to think that Lily might not like him anymore. "Think of something else – "

"No, it's all right." Remus sighed and rubbed the back of his neck. "I'm sorry. You're just trying to help. This whole thing is just sort of…stressful, you know?"

"I know," said James, thoroughly relieved that Remus seemed back to his normal self, though he still felt on edge himself. "But it'll be all right. We'll get Snivellus kicked out and you'll be safe."

Something flickered in Remus's pale eyes – discomfort? Guilt? – but James couldn't read it.

"Moony," he said, "we can think of something else. This isn't the greatest plan ever anyway – "

"It's fine, Prongs," Remus interrupted. "Like you said, it'll be all right."

"Yeah," said James, unconvinced. "I'll…er, see you in the dorm later, then, shall I?"

"Sure," Remus responded, easily enough, James thought as he descended the stone steps from the Astronomy Tower.

It was only when he was halfway back to Gryffindor Tower that he realised that talking to Remus hadn't comforted him one bit. If anything, he felt worse.

Half an hour was a long time to be checking the Astronomy Tower.

Lily didn't know for sure it had been half an hour since she and Remus had separated in the usual way, of course, because her Muggle watch didn't work at Hogwarts. She did know, however, that she had checked the entirety of the fourth floor three times and her fellow Prefect had yet to return to meet her before they proceeded down to the dungeons together. It was a routine they'd fallen into sometime back in November, when they'd realised they could save a lot of time if they did parts of the castle alone. It was bending the rules, of course – two stern faces were considered much more effective than one when faced with late-night delinquents – but they'd quickly worked out which the quietest places were and those were the ones they tackled single-handedly, as quickly as they could.

Which meant that Lily was somewhat bemused as to why Remus was taking so long: it had been ages since they'd caught anyone in the Astronomy Tower, and even then it had been two snivelling third years lacking any greater imagination, who didn't need telling twice to get back to their dormitories. He hadn't been held up by troublemakers, surely.

She waited at the top of the staircase, their usual meeting point, her elbows resting on the bannister as she drummed her fingernails on it, thinking about the long Charms essay awaiting her back in Gryffindor Tower. Where was he? Should she go and find him? Her nose wrinkled at the thought of the number of stairs she would have to climb before going all the way back down to the dungeons. The idea was not appealing.

Still, she thought, what if he's in trouble?

It crossed her mind that this was, perhaps, the central reason for why they were supposed to patrol in pairs.

Lily's eyes drifted up the next staircase. Maybe she had missed him somewhere along her second or third check of the fourth floor. Maybe he'd gone down to the dungeons without her.

Well, if her Charms essay was ever going to get done that evening, she ought to head down to the dungeons anyway. She might, after all, miss Remus if she went up to the Astronomy Tower. If he was still up there, he'd work out she'd gone down without him and she could meet him there. It was their very last place to check, so if Remus didn't appear, she'd check the Astronomy Tower on her way up to the dorms.

Remus wouldn't like this, a small voice said in the back of Lily's mind as she straightened up. They had never, ever caught anyone in the dungeons (possibly because it was the least romantic place in the whole castle), but Remus had always insisted they do it together – in no small part, Lily suspected, because the Slytherin Common Room was in the dungeons. Still, Lily thought indignantly, she could handle herself just fine, thank you very much. She didn't need someone protecting her. Besides, the chances of running into anyone were fairly remote.

Pushing the doubts from her mind, Lily started to descend the staircase.

She regretted her decision as soon as she stepped off the last stone step and into the dank atmosphere of the Potions corridor. Lit torches flickered on the wall, but there was no natural light from the stars here: the shadows loomed large and dark everywhere. She had never been down here at night by herself, she realised – even on the occasions she attended late evening parties in Slughorn's quarters, Alice and Dorcas were always with her.

"Remus?" she called softly, suddenly unwilling to draw attention to herself but keen to find her friend.

Silence. Involuntarily, Lily shivered. It would be easy to go up, she knew. She could wait for Remus in the Entrance Hall – he had to pass through there to get to the dungeons. But he might already be here. He might not have heard me. Besides which, there was a stubborn part of Lily that refused to back down.

Honestly, she scolded herself. What are you afraid of? Everything she might have once been afraid of – ghosts, poltergeists, monsters in wardrobes – it was all real and she knew she could handle it. So are you a Gryffindor or what?

She pulled out her wand and lit it. The light was bright, but not bright enough to see all the way down the corridor. Her heart was hammering painfully against her ribs, but gritting her teeth with newfound steel, Lily stepped forward, wand out ahead of her.

The truth was she had been afraid of the dark as a child. It was, in fact, how she had discovered she could do magic: her parents, keen to keep their electricity bill cheap and no doubt tired of Petunia's incessant whining that she couldn't sleep with the light on, had insisted one night when Lily was six that when it was time for bed, the light had to be switched off. Lily had cried and cried until she had seen a burning red behind her eyelids and had seen a white ball of light hovering above her bed. Perhaps she ought to have been afraid, but instinctively she had known that the light meant her no harm.

"Petunia, look!" she had squealed.

From the next bed, Petunia's sulky voice had emerged out of the darkness.

"Go to sleep, Lily."

"But, Tuney, look at the light!"

"Are you daft?" Petunia had asked. "Mum and Dad said no lights. That's why it's dark tonight." Suddenly her voice took on a suspicious edge. "Why aren't you crying anymore?"

"Because there's a light," said Lily, bewildered. "Can't you see it?"

"See what? It's pitch back, you idiot." The sound came of Petunia rolling over. "I knew you were pretending this whole time."

"Pretending what?" Lily asked, but the stubborn silence told her that her sister was determined to go to sleep. Frowning, she looked up at the ball of light. Could Petunia really not see it?

The answer had to be yes, she knew, because even if Lily had opened the curtain a crack to let in the light from the street lamps, Petunia would have been downstairs whining to their parents.

She had thought at the time it must be some sort of guardian angel only she could see. Now, of course, she knew better. She found herself wishing, suddenly, that coming to Hogwarts had not meant that she lost most of her involuntary magic. She wouldn't have a clue, now, how to cast that sort of spell, or even if it actually existed.

Practise, Severus had told her. You have to practise to learn how to control your magic. And he had shown her how, and now she could still spin a daisy chain without touching it. But as she'd never actually confessed her fear of the dark to Severus (how mortifying, at ten, to want to sleep with the light on!) and coming to Hogwarts had largely expelled that fear anyway, she could no longer create her ball of light as she once had.

That's what Lumos is for, Lily told herself sternly. Grown-ups don't need a ball of light.

Still, the unsettled feeling in her stomach kept her moving – she wanted to get out of the dungeons quickly The Potions classroom was empty, save for twenty cauldrons fermenting in a corner. A cupboard Lily forced herself to open revealed nothing but Filch's brooms and mops. Slughorn's office was dark, the door closed – perhaps he was in his private quarters at the back. His was the last room down in the dungeons; heart filled with relief, Lily turned to leave.

It was then she heard voices.

Quiet, muffled voices, admittedly, so that nothing distinct could be heard, but it still made Lily whip around, wand outstretched, pulse racing wildly as she squinted ahead of her. But there was nothing. Of course there wasn't – she'd just looked, hadn't she? – but as she moved her wand ahead, she saw there was another bend in the corner. Dimly, she remembered it, but she and Remus never bothered to check there because there was just a blank wall. But around a corner, out of sight, was the perfect place to avoid getting caught, thought Lily, and clearly someone had realised it. Crossing her fingers it wasn't seventh year Slytherins, she crept forwards and turned the corner.

There was no one there.

Or, rather, she couldn't see anyone: there was only a short space between the corner and the blank stone wall she remembered and it was empty now but for her and an abandoned pile of cauldrons. But the voices were louder now – still muffled; she couldn't hear them properly – but definitely there.

"Homenum Revelio," Lily whispered, raising her wand.

Nothing. She was alone in that small space. Which meant….

Slowly, she took several steps forwards, towards the wall, before lowering her wand to her side and pressing her ear against the cool stone.

"There's a perfect justification for it, can't see why everyone doesn't know about it – "

"Well, we know Mudbloods and Muggles taint a bloodline, make it less powerful – "

Lily's heart dropped to her stomach. The voices sounded vaguely familiar, but she couldn't place them: she could make a reasonable guess as to the sort of people they were, though. She grimaced, still shocked and bemused after years of Hogwarts that some people could think like this.

"But there's a really clever Mudblood in my class!"

This voice sounded much younger: Lily would have placed the first two in sixth or seventh year, but this voice was not yet broken – perhaps only a second or third year.

"Pretences!" said another deep voice. "Mudbloods have been pulling the cloak over our eyes for years! Haven't you heard the story of the Monied Mudblood and the Pauper Pureblood? It starts with a pureblood – one of the Sacred Twenty-Eight – who had fallen on hard times – "

"That's just a fairytale for kids," said a scornful voice.

"Look here, my great-grandfather wrote that and if you're calling him a liar – "

"Cantankerous Nott was stark raving mad by the end – "

"How dare you – "

"That's enough! A hard voice, which had not yet spoken – much colder than the voice of Rowan Nott, who Lily realised must have been speaking – broke in, and the murmuring ceased somewhat, but not entirely. "We are not here to discuss the merits of bedtime stories. We're here to get on with the discussion. The title of this evening's meeting is 'Sterilising Muggles: Methods and Concealment'."

Lily's blood turned icy: she suddenly felt numb. She had never heard of such a thing – sterilising Muggles against their will, eliminating Muggle children, Muggle-born witches and wizards... How could people be discussing it here, at Hogwarts? Had she really been so naïve to assume that they were safe at Hogwarts – that all the really nasty stuff happened outside the castle walls? But even in her worst nightmares she had not thought something so hideously awful would be contemplated…

Who were these people? Nott, obviously, but who else – who else would involve themselves in this? And where were they? They were not in the Slytherin Common Room, which was far away from here. No, it had to be some sort of hidden room, some sort of meeting place for these sick individuals.

She had missed the next few sentences. Shaking slightly, she bent her ear to the wall again.

"-the author of the book in our collection on this subject suggests the Barren Curse – developed by the distinguished Sirius Black I – equally effective on Muggle and Mudblood women, though the main drawback is the precision required. The author recommends the woman be restrained in an accessible – "

No. She couldn't listen. Letting out a strangled cry of disgust, she tore her ear from the wall, staring at it in horror. She had to tell someone – Professor McGonagall; anyone…Her legs felt weak as she backed away from the wall, her mind spinning. But suddenly her foot caught something underneath her, she was falling, and the pile of cauldrons she had stumbled into collapsed with several loud crashes. Lily scrambled up, grappling for her wand, but it was too late: she could hear footsteps and voices telling someone to investigate…

She had just made it to her feet when she heard three taps and, suddenly, as she stood rooted to the spot, she saw one stone near the top edge inch out towards her, before the whole wall started to crack down the middle, edging apart, just wide enough to reveal and very familiar looking figure with lank hair and a thin stature.

Lily could only gape, but the person wasted no time; he started forwards and grabbed her roughly by the upper arm, before pulling her around the corner. He threw up a Muffliato charm before whirling around to face her.

"What are you doing here?" he demanded.

His voice started Lily out of her reverie. "What am I doing here?" she said furiously. "What are you doing here, Severus Snape? Those people are sick, and if you – "

"Snape, what is it?" someone called – Lily thought she recognised Avery's voice.

"Shut it, you fool!" Severus whisper-shouted back. "You'll get us all into trouble! It's just Filch's cat with her damned kittens again!"

"Well, come back, then!"

"I'm moving them so Filch doesn't come snooping," Severus returned. Her whipped back to Lily. "You've got to go; they'll kill you – "

"I'm not going anywhere," said Lily icily, crossing her arms, "until you tell me what's going on!"

His expression was torn, anguished.

"Severus," Lily hissed.

"There's no time," he said, pushing her a little. "Tomorrow."

"Tonight," Lily insisted. "Tonight, or I'm going straight to Professor McGonagall. I should do that anyway – "

A flicker of something – fear? – crossed Severus's face.

"Transfiguration classroom at midnight," he said. "Now go."

Reluctant to leave, but recognising the concession for what it was worth, Lily nodded. She backed away. Severus gave her a last piercing look, before disappearing around the corner, leaving Lily with her spinning thoughts and churning stomach.

She'd thought he might not show, but he was there before she was, still dressed in his school uniform as Lily slipped into the classroom in her nightgown. She felt cold and hideously underdressed for wandering around the school, but she had not had much choice – failure to go to bed would have made her friends ask questions, and she could hardly tell them the truth.

"You're late." His voice was low as she shut the door softly behind her.

She turned to face him, pulling at her dressing gown cord to make it tighter. "I don't think you're the one to be lecturing me right now," she said coolly. She waited for him to speak, but he seemed intent on studying the desk in front of him. Well, she thought,she wasn't about to make this easy for him. She folded her arms and waited.

"It's not a big deal," he said finally.

Whatever Lily had expected, it was not this. "Not a big deal?" she burst out in a furious whisper. "Sev, this is serious! How could you? What is it – some sort of anti-Muggleborn cult you've all created?"

"Don't be stupid," he said, his dark eyes rising to meet hers. "It's nothing like that. We just meet to discuss things – "

"Like sterilising Muggles and Muggleborns?" Lily's voice was rising. "People like me, Sev?" She felt physically sick, but she was rooted to the spot in her disbelief. She was no stranger to the fact that all of Severus's friends were into the Dark Arts, but she'd been foolish enough to think that Sev was keeping out of it – that he wasn't the same.

Severus looked pained. "You know it's not like that," he said. "I would never – you're too – " His gaze snapped away abruptly to the wall. When he looked at her again, his expression was blank, unreadable. "The seventh years started it," he said. "It's been going for years – meeting occasionally to discuss Dark Arts. You're just expected to join. My friends – "

"Oh yes, I suppose Avery and Mulciber are in it," said Lily scornfully.

"All my year are in it," said Severus. "How do you think it would look if I wasn't?"

"If you had any decency, you'd go straight to Dumbledore and get it stopped," said Lily.

"I'm sure that would go down splendidly with the people I have to share a dorm with for the next two and a half years." Severus's voice dripped with sarcasm.

"Then I'll go to Dumbledore," said Lily hotly. Her vision was blurred with tears. What had she expected? That Severus had some way of explaining this? It was too awful to be explained – she should have known that. She turned to go, wiping her face angrily with the back of her hand.

"I'll be expelled."

Lily's hand hovered over the doorknob, and she turned slowly to face her childhood friend. His face was white; she knew what it had cost him to say it, to admit this weakness. She had never seen it as a weakness, but Severus certainly had, and he hated even alluding to the fact that his home life was less than ideal. But Lily well knew expulsion for Severus would be punishment far beyond what he deserved – while, she was sure, the likes of Avery and Nott would get off because of family influences. Could she do that to him?

"I'll leave your name out of it," she said.

"They'll tell," said Severus, and his tone was wretched. "And they'll know it was you if I'm not landed in it too."

"I don't care about that."

"I do," said Severus, so quietly that Lily wasn't sure she'd heard correctly. She stared at him, understanding that he was asking her to keep this to herself – not to tell anybody.

"How can you stand to listen to it?" she asked softly. "Sev, they were talking about people like me and my parents like we're…like I'm…" A lump had formed in her throat, preventing her from voicing her fears: that there was a substantially larger proportion of people than she had realised who thought her worthless, who wanted to hurt her…that those people might include Severus…

"I don't like it any more than you do," he said quickly. "You know I think you're the best witch in our year – probably in the whole school. But…but it's better like this, isn't it? Knowing what people out there are really like, knowing what we're up against? That's the only reason I sit there and listen to that stuff, Lily."

She wanted to believe him. He was gazing at her earnestly and she had to look away.

"But you are interested, Sev," she said. "You can't deny that. I heard them talking about a collection of books – you've read them, haven't you?"

Surprise flickered across Severus's face – perhaps at how well she knew him. "Yes," he said, his tone cautious. "All the stuff we talk about comes from the books they keep in that room. I feel obliged to educate myself."

"How could you? They deserve to be burnt!"

"No book deserves to be burnt," said Severus, jutting out his chin. "I told you – I'm only interested to know what's out there. Knowledge is power, after all."

Evidently he meant this as a rather grandiose statement, but it made Lily shiver.

"That's probably the sort of thing You-Know-Who goes about saying."

"That's the sort of thing Slytherins go about saying," Severus corrected. Lily was silent. He took a hesitant step forward. "So…you won't tell?"

"It's sick," said Lily stoutly, folding her arms. "Frankly, Sev, whatever your motives, you all deserve to be expelled."

"Says you," Severus retorted. "I say everything deserves discussion, whether you agree with it or not." His eyes suddenly seemed blacker, his expression cold. "I thought you were open-minded. Not like your sister."

It was a low blow and he knew it: Lily could see the apology in his eyes before he opened his mouth again. She waved it off.

"I am," she said. "But I'm worried that for the rest of them it isn't, you know, academic." As the words left her mouth, she realised she had just inadvertently suggested that what Severus was doing was perfectly acceptable. Was it? Remembering the discussion she had overheard still made her shiver. But one of the things she had always admired about Severus was his intellectual curiosity – his interest in possessing knowledge for the sake of knowledge. And he was right: she certainly could not argue with the view that it was worth knowing what was out there, rather than staying in ignorance.

"Most of the others are too stupid to comprehend most of what goes on." Severus's tone was dismissive, but he must have been able to see that Lily was still tense because he added, "Seriously. It's not like they could do this stuff under Dumbledore's nose, is it?"

"I guess not," said Lily slowly, reluctant to make any further concessions, any agreement. The thought that people like Nott knew how to hurt her so badly made her insides twist horribly, even if they couldn't use it at school. "I still don't know if I can keep this quiet, Sev."

Something in Severus's face closed up; he turned away slightly. She hated it, knowing that he didn't trust many people in his life and that she was compromising his trust in her.

"As you will." His tone was bitter. "I thought you were my friend."

"I am, Sev; I just don't like you mixed up in this stuff."

"I'm not mixed up in it. It's just something the Slytherins do. Like the Gryffindors sit around eating toasted marshmallows and playing Gobstones." The sneer was just barely detectable, and Lily almost blushed, because it was typical of Friday nights in the Gryffindor Common Room. "You wouldn't understand," he said bitterly.

He had been saying that more and more lately; and perhaps it was true. She certainly couldn't imagine her House-mates sitting around discussing Muggle sterilisation techniques with interest rather than outrage. She wrung her hands.

"If I don't say anything – " He looked up, hopefully, and she made sure to hold his gaze. "You've got to promise me it's not going any further."

"We're not exactly planning to broadcast it," said Severus dryly.

"That's not what I mean. I don't want you going around using this stuff on Muggle Borns, Sev."

"I won't. I promise."

It was said a little too quickly; a little too easily. Lily surveyed her friend, trying to work out the loophole.

"But the others…" She trailed off hesitantly.

"They won't hurt you," said Severus. "I promise. I won't let them lay a finger on you."

It was not herself she was concerned about, but Severus's gaze was so intense she felt embarrassed; it had suddenly turned awkward; they had strayed into something she hadn't banked on. She lowered her eyes, flustered, trying to find a way to handle this safely and drawing a blank.

But she already knew one thing. She couldn't turn him in. Not to be expelled. And so long as they didn't use this stuff… She was not binding herself in any way; if they used it, she could tell Dumbledore what she knew…

"All right, Sev," she said at last. "I won't tell."

Severus's face lit up; she thought for a moment he might actually hug her. But even Severus's obvious delight couldn't help her shake the feeling that she was doing something very, very wrong.

"I need to go to bed," she muttered, fumbling for the doorknob. Her eyes were burning again; she could hardly see. She felt the handle underneath her fingers and fled before she could say another word, before she broke down into tears.

Severus watched her go, chewing his lip nervously, his heart hammering. He knew Lily was good for her word – if she said she wouldn't tell, she wouldn't, but with the threat of expulsion gone he was suddenly left to confront the horror he had felt when he had discovered Lily in the dungeons.

Thank Merlin it had been he who had checked on the noises outside and not someone else! His House-mates had enough quibbles with Lily Evans to justify them teaching her a good lesson. Severus wasn't sure Lily had comprehended how much danger she had been in – how much danger she would be in, if she did tell after all. He, Severus, would be expelled, but many of them wouldn't, and they'd see to it that they got revenge on the individual that had told on them in the first place. Whatever he had told her, some of the Slytherins were definitely stupid enough to use the curses they had learned during their meetings. Severus had known well enough that sort of threat wouldn't go far with Lily – she could be the most foolhardy of Gryffindors at times. Luckily, Lily's kindness was as predictable as her bravery, and he had half-suspected, half-hoped that he could appeal to her successfully, even if he had had to betray his weakness to her.

He thought of his parents' dilapidated house in Cokeworth, with its grimy windows and roof badly in need of repair, and grimaced.

None of this, of course, solved this little problem with Potter. He may have avoided drawing further attention to Lily, but the Slytherins were already keenly aware of her recent affinity with the Gryffindor Chaser. He had promised himself he was going to talk to her today, but she'd been surrounded by her friends in the library all day, and she'd rushed off just now before he could even bring up the subject of Potter.

Tomorrow, he thought resolutely. It had to be tomorrow; he could not keep putting it off like this. If he was not careful he would run out of time and she would be dating Potter.

The thought made him want to throw up.

A/N: As always, I would love to hear what you thought. The next chapter may take slightly longer but is well on its way (and reviews go a long way towards speeding me up!).