Moonlight settled like white dust across the turrets of Hogwarts—the very semblance, or so it seemed, of peace. Four shadowed figures stood at the main entrance, paused on the steps as though discussing something. Their faces were hidden by billowing hoods, and their postures were tense. A quiet, cool breeze stirred their robes, and the tallest one among them raised a wand. There was a small glow of light after a whisper of Lumos, and the figures made their way into the school.

'Bloody Merlin!' Severus Snape threw down his gloves in frustration—nearly toppling the tiny bottle of bubotuber pus that sat, uncapped, on his worktable. It stank maliciously. Snape, hair even greasier after an hours-long bout of brewing, snarled at it incoherently. A smoking and rather burnt-looking cauldron rolled at his feet. The dungeon's stale air had that echoing quality to it—the kind that follows an explosion.

'Bloody pus, had to decide to desensitise the wolfsbane two minutes early, you couldn't have waited, could you, you uncooperative stinking excrement—'

His hands were stained. More than usual. His robes were charred. And his face—his face—ached as though it had been scowling for five hours continuously, which, according to the timid clock, it had. Said clock almost seemed to sink into the wall when Snape narrowed his glare at it. Its hands literally quivered. Five hours. Five hours of brewing the bloody thing, and it had to go and—

Snape cursed and swung around to face the bottle again. Only five millilitres left. He ground his teeth. He'd have to go and see that airhead Sprout again, and spend two hours cozening up to her fucking orchids before she'd let him have more of that pus—an especially potent batch that she milked for her own purposes, and that couldn't be bought cheaply at any of the… less popular… shops Snape visited at Knockturn.

Damn.

It was three a.m. in the morning. Severus Snape had been awake for twenty-nine hours. His eyes prickled with the after-effects of Pepper-Up, and his large nose twitched reflexively after hours of painful sniffing. Snape waved his wand, and levitated the cauldron back onto its stand.

His latest project had been a failure. And. His. Pus. Had. Just. Run. Out.

Perhaps that would explain his state of mind when, upon hearing a knock on his door at this ungodly hour—although to Snape all hours were ungodly—he didn't immediately think to summon Dumbledore. It had been years, after all, since anyone had threatened Snape personally at Hogwarts—strongly warded as it now was against the Death Eaters, and emptied of any resident mutts and werewolves. So, expecting yet another fifth-year Slytherin girl in need of post-coital contraception, or a first-year with nightmares (although why they thought he could comfort them, he never knew), Snape stabbed his wand at the door and muttered 'Open' even before he turned around, still thinking of bubotuber pus and orchids.

It was something of a surprise, to say the least, when he turned to see four Aurors standing in his doorway. Ministry insignia shone on their robes—and Snape, with the sort of prescience only a twice-incarcerated ex-spy could have, felt his bones turn to ice.

'Professor Snape,' said a deep voice, and Snape looked up, startled, into the familiar face of Kingsley Shacklebolt. The tall man stared back at him as if he were a stranger. Calmly. Snape opened his mouth to ask: Why are you here, but a smaller witch stepped between them, an alarmingly Slytherin smirk twisting her mouth. Snape's fingers twitched on his wand. He knew, from experience, that it would do him more harm than good if he was outnumbered.

'Severus Snape,' she sneered, in a voice so reedy it nearly made him wince. 'You are under arrest.'

A few years ago, Severus would have screamed 'I'm WHAT!' before letting loose a volley of invectives (and hexes) enough to bury any man alive. Now he only stood frozen; the shock echoing through his chest not unlike the explosion that had rocked his quarters a while ago. A peculiarly calm sort of rage tightened his throat. His heart seemed to have stopped altogether. He'd thought this was over. Years ago. He hadn't done anything since then. Anything. He hadn't—

Ah. But the past always would come back to haunt him, wouldn't it? He looked at the silent Shacklebolt—a man he'd thought of as an ally, a fellow member of the Order. But now…

'On what charge?' Snape asked with forced calm, turning back to cap the bubotuber pus as if nothing had happened. He was cold all over—his hands were almost shaking—but he wouldn't give them the satisfaction. Azkaban, his mind whispered, and a sudden image of Black—hollowed face, wild eyes—flashed past his eyes. He flinched.

The witch spoke up again. 'For sedition against the Ministry and conspiring with Death Eaters, of course. You well know the charges, Snape, so stop pretending.'

Stop pretending. Snape nearly laughed. I stopped doing that years ago, when I stopped spying on Voldemort. He still didn't turn around. 'I had been arrested on those charges twice before, if I recall,' he said as he walked over to his shelves and carefully placed the pus next to the powdered foxglove. 'And cleared both times.'

There was a silence. Snape turned to see the witch unrolling a scroll. 'We have received,' she said snidely, 'new evidence.'

'New evidence.' Snape's voice was flat.

'Yes. The case—', here that ghastly smirk reappeared, 'has been re-opened.'

'Re-opened,' Snape repeated again, voice not quite so flat anymore. His vision was swift becoming tainted with red and—good sense or not—his wand was starting to feel decidedly hungry.

'Good to see you as eloquent as you always were, Severus,' said another voice dryly, and Snape glanced over to see the third wizard lowering his hood. If Snape hadn't already been so strung up, he might have been surprised to see another familiar face—this one from his schooldays. Julius Abernathy, Arithmancy prodigy nearly thirty years ago at Hogwarts, and Snape's only classroom rival. A conniving, sharp, utterly heartless Ravenclaw—and also Snape's erstwhile lover.

'Abernathy,' he greeted coldly. So this is what the bastard's been doing.

'Severus,' said Julius, slightly more warmly, although his quiet smile had something of an edge to it. 'I'm afraid what Tabitha said is true.'

Tabitha. Snape glanced over at the reedy witch, who puffed up importantly. Brainless pigeon, he thought, and something of his sentiment must have shown on his face, because she frowned.

A chuckle drew his attention back to Julius. 'Same as ever.' The man—irritatingly handsome after all these years, even though the pale gold of his hair had dulled to grey—strolled up to Snape's worktable. Reached out his fingers.

'Don't. Touch. My. Potions.'

Abernathy raised an eyebrow. 'And possessive as well. You haven't changed at all.' But his hand retracted from the bottles post-haste.

Snape scowled. 'I'll thank you to tell me the charges in detail, Abernathy. I'm sure you won't mind a trip down memory lane later, when I'm behind bars.'

Tabitha nearly opened her mouth, but Julius waved her silent. Ah. A superior. 'The thing is, Severus, we aren't quite sure we should arrest you. Yet.'

Snape's scowl deepened. 'What the bloody Hell do you mean, Abernathy? You just said—'

'That we have new evidence, yes. And that your case has been re-opened.' His eyes sharpened. 'But you see, Severus, there is something you can give us. If you cooperate, you may not get arrested after all.'

A bubble of incredulous mirth almost found its way out of Snape's mouth—he bit his tongue to stop it. Cooperate? So this is what it's about. Suddenly, Snape felt a lot calmer. He also knew, with sudden clarity, that it was highly unlikely the Ministry had—he sneered to himself—new evidence. They just needed him. For something. The arrest was a threat they were hanging over his head in order to force his cooperation—but an arrest wasn't what they really wanted.

And if there was one thing Severus Snape knew, it was that cooperating with other people's desires was often the quickest way to attaining his own. Provided they were… compatible, of course.

He felt his face settle into the comfortable grooves of his sneer, and saw the fourth wizard—the one as yet still hooded, and quiet in the corner—draw himself up.

'You want something. From me.' Snape let his eyes rest on Abernathy again. The bastard was smiling.

'I see you understand. I knew you would.'

'What it is you want?'

Abernathy paused--tilted his head so that the firelight shadowed his face. 'A potion.'

Snape felt his throat click in response. Hope surged in his heart—this looked so fucking easy all of a sudden—but he knew—he knew—it couldn't be that simple. His life for a potion. It must be one hell of a potion. 'And what,' he asked, forcing his voice to tense courtesy, 'is that potion for?'

Abernathy's demure smile tightened. 'Three guesses, Severus. And the first two don't count.'

There was a silence in which they stared at each other—Snape barely seeing Abernathy's face as the only real possibility ran through his mind, unlikely though it was. It was glorious—it was stupid—it was so very, very much like the Ministry. Finally, his shoulders relaxed. 'You want a potion,' Snape replied, 'that will kill Voldemort.'

Abernathy seemed to relax as well. 'Exactly.'

'You do know that's impossible.' Or you'd have brewed it before.

'Not quite.'

Snape glared at him.

'We have… made a certain discovery recently. The potion will not be for Voldemort himself. Rather, it will destroy his… army.'

Snape felt his eyebrows rise in spite of himself. 'His army. You mean—'

'The horde of Dementors guarding him, of course.'

The Dementors… Every single one of them in existence—a soul-sucking army so massive that it formed an impenetrable wall even against the Ministry's entire legion of Aurors. Those Dementors were the main reason, given the recent apprehension of most senior Death Eaters, that Voldemort was still alive. But this-- 'This is insane.'

Julius actually laughed. 'Yes. Yes, it probably is. But you see—we have a genius on our side. The one you'll be working with. He'll supply the ingredients, and the design. You—', here Abernathy made a stirring motion with his hand—'simply do what he tells you.'

'A genius.' Oh, this was getting better and better, wasn't it? 'Either you've gone mad, Abernathy, or your genius is concocting some sort of myth. You're planning to brew several hundred gallons of an impossible potion—an anti-Dementor potion, for Merlin's sake—and then feed it. To the Dementors. Ha. Perhaps you'll ask them over for tea?'

'And perhaps you don't understand after all, Severus,' Abernathy said in that irritatingly self-sufficient tone he'd often used at school. 'The potion isn't for the Dementors at all.'

Snape's brow furrowed.

'It's for us.'

Silence. The firelight flickered. Snape realized that his jaw had dropped—an extraordinarily rare occurrence—before he snapped it back shut again. 'That--it--how?'

Abernathy looked inordinately pleased with himself. 'Unfortunately we can't tell you any more until you're in our custody.'

Snape hissed in irritation and whirled about to stare at his potions. Row after row of bottles, stacked in little black boxes on his worktable, and in equally neat rows on the shelves above. They glinted comfortingly in the firelight. The Ministry wants me to… They want… the impossible. It can't be done. It can't. They'll have me—they'll have me anyway. The bastards.

'Why—did you choose me?' Snape found himself asking. 'Surely—'

'Because he asked for you.'

'He.' Severus turned around slowly again; fixing Abernathy with a gimlet eye. 'He. Your genius?' He even forgot to infuse the word with contempt.

Julius nodded.

'And what,' Snape ground out, 'might be this genius's name?' So that I might carve it on his epigraph before I choke him to death.

Abernathy only smiled. 'Ah,' he said, 'that's still classified, Severus, until you meet him. He asked for you because he said you were as gifted at Potions as he is at... Well. You'll find out. Until then,' the smile curled into a smirk, 'you may call him the Green Knight.'

Snape's jaw threatened to drop again. 'The Green Knight. You've got. To be. Joking.'

'I'm not. You'll see why the name suits him, though.'

Knight. Don't tell me he's a Gryffindor… But green. Relief. 'He's a Slytherin.'

'No.'

A Gryffindor, then. Shit. At least that explained the suicidally stupid nature of this plan. 'I don't have any way out of this.'

A placid shake of Abernathy's head. 'None whatsoever.'

'I could get sent to Azkaban if I don't cooperate with your hare-brained, toxic and possibly suicidal scheme.'

'No need to sound so negative, Severus. But… yes.'

'I have to leave my dungeons.'

'Yes.'

'I have to leave my potions.' Snape was starting to realize, distantly, that he sounded like a child. It didn't help his mood.

'Indeed.' Julius' mouth was curving up in that charming—augh. Tabitha tittered.

'Fuck you, Abernathy, and fuck the Ministry.'

A slow grin spread across Abernathy's face. 'I'll take that as a yes. And you'll truly enjoy the project once you get started. Such a challenging potion, after all...'

Snape grunted. His hands were still dangerously close to shaking. 'I will not be harmed in any way?'

'No. We do need you, Severus. Provided you cooperate.'

He drew a breath. 'I want to see the Headmaster. You can't just take me--'

'We can. Your door's wards didn't warn you about us, did they? We're authorized Ministry personnel. We can enter Hogwarts, and we can leave... But we'll be courteous, since you've been so courteous as well. We'll let you see Dumbledore first.' Abernathy waved his hand, and the fourth, still-cloaked Auror stepped forward. 'Bind him.'

Snape nearly whipped out his wand--but the look on Julius' face warned him.

'No games, Severus. You might be working with us, but we've got to make this look like a standard arrest. Dumbledore approved.'

Shock at that--deepening disbelief. 'No. No. Albus wouldn't. He--'

'He did. It was arranged for us to come tonight, to pick you up. It was he, in fact, who requested that Shacklebolt be here.' Abernathy spared a puzzled glance for the tall Auror, who stood expressionlessly next to him, sole earring glinting in the dull light. 'Don't ask me why.'

An invisible, but nonetheless tight, wire began to bind Snape's hands behind him. The faceless Auror appeared to be whispering a spell. Snape suffered the indignity, mind racing. Albus wouldn't do that to him--he was, if not a friend, at least an ally--for fuck's sake, the man had testified to keep him out of Azkaban two times already, and why would he--

Unless--

'He agrees.' Abernathy was looking at him again, eyes disconcertingly sharp. 'He is the only person outside of this project who knows about the Green Knight, and the potion you are to make. It may very well be the end of Voldemort, Severus. That's why--'

'Albus agrees. I see.' The heat of anger, and the cold of fear, had both left Snape like the flow of bad blood. He tried not to feel betrayed at Dumbledore's involvement--tried not to feel, desperately, that he was being snatched out of the only refuge he'd known for years. There was a peculiar silence in his head--the kind he recognized from his initiation into the Death Eaters--a sense that he was getting into something he would regret, and yet was completely helpless to stop. Snape glanced around his dungeon one last time. He took in the sight of his beloved potions, the singed old rug, and his large oak desk cluttered with quills and parchment. He breathed in, for what might be the last time in his life, the comforting, dank scent of his dungeons.

'Are you ready?' Abernathy was already at the door, glancing back. The fourth Auror prodded Snape in the back with his wand.

Snape nodded. 'You will take me to the Headmaster first.'

Tabitha, restless at having stayed silent so long, piped up. 'Just be grateful we're obliging you, Snape. Death Eaters like you don't deserve a second chance.'

'Tabitha.' This spoken sharply, but not by Julius. Shacklebolt had taken up a stance before Snape. 'We will escort him. But you. Will be. Silent.'

The witch looked stunned.

Snape thought he caught a hint of apology in Shacklebolt's eyes--but it might have been a trick of the light, or wishful thinking. Snape had been a spy, after all--he knew that, even were Shacklebolt his colleague in the Order, they couldn't appear to be familiar here. Abernathy was not to know. In a sense, Shacklebolt's silence was reassuring.

Then again, it was not.

The clock chimed four with its trembling hands. Snape, as he was lead out by the Aurors, didn't even spare it a glance.