Severus Snape turned sharply. "Did you hear that?"

Longbottom frowned. "What?"

Snape was still for a moment, head tilted to listen. "I thought … no. Nothing." He considered putting the Invisibility Cloak back on. No. What he had to say could only be said face to face. Circe curse Granger and her infernal Muggle ideas. 'Clear the air with Longbottom', indeed.

And Circe curse me for agreeing to try it.

But he had, and so the words had to be said, however foul they tasted in his mouth. "Longbottom, I'm sorry about your parents."

"Thanks," Longbottom said. "You would have warned them, if you'd known, I know that now."

Snape shook his head. "I made no effort to find out. If I had know … I might not have bothered to warn them, warn Dumbledore. I … after the Dark Lord's fall, I didn't … my vigilance was not what it should have been."

"You were grieving, I expect," Neville said easily. "It's like that. Like having your own personal Dementor. You know you should get up and do something about breakfast and talk to people, and then it's six in the evening and you just go back to sleep."

"And how would you know?"

Neville glanced at Snape. "Fifty of my friends died on one day, you know. I have some experience of how it feels."

Snape closed his eyes. "Yes." The words burned like bile in his throat. "Yes, I should have … again, I apologise."

"Me too," Neville said. "For hating you, all those years."

Anger flared through Snape's veins. Longbottom, apologising to me? Neville Longbottom,daring to be sorry? "I meant you to," he snarled. "And if you're about to say you 'should have known', Longbottom, I remind you that I successfully deceived one of the most powerful wizards in the world for years."

"That's true, and I don't think it was particularly thick of me not to realise you weren't loyal to Old Voldy, but it's still not very nice to be hated."

"On the contrary," Snape said. "I entirely enjoyed it. Don't assume I was hiding any fond feelings for you, Longbottom, or for Potter and his friends either. You were an utterly frustrating student, perhaps the most infuriating I ever had the misfortune to teach, and if I were forced to chose whether you, the Dark Lord, or Albus Dumbledore were more of a thorn in my side, I would have to think carefully."

Longbottom grinned. "Are you saying I'm your Boggart, as well?"

Snape narrowed his eyes. "If incompetence had a human form, you might well have been."

"I scraped an 'A', didn't I?" Longbottom said.

"You should have achieved an 'O'," Snape snapped, "and you would have, if you'd applied yourself."

"And it's still so hard to understand why Hermione won't let you near her students."

Snape glared at him. "Five points from Gryffindor for cheek, and another ten for such a feeble effort."

"Fifteen points from Slytherin for managing to bugger up a perfectly acceptable apology," Longbottom shot back, "and you should remember, Professor, I'm actually the only one of us able to deduct points."

"You wouldn't …"

Longbottom laughed. "No, it'd be a bit hard to explain, wouldn't it? Speaking of, you'd better get back under Harry's cloak before a couple of sixth years looking for a quiet place to snog get the fright of their lives."

"Deservedly," Snape said sourly, but he shrouded himself in the Invisibility Cloak again. "I suggest the west side upper corridor. If you approach quietly enough, the students are sometimes sufficiently startled to scream aloud."

"I don't particularly enjoy making children scream," Longbottom said. His voice was even but there was a note in it that made Snape wince.

Glad he was well and truly hidden from view, he made his voice carry the old mockery and malice. "Then you clearly haven't been teaching very long. Give it a few years, Longbottom, and you'll be looking kindly on Filch's request to reinstate the cat'o'nine tails."

He moved away before Longbottom could say anything else. That's right, Professor Longbottom. Don't forget for a moment that I'm the Headmaster whose rule saw the Cruciatus curse used on students. Make your jokes, and treat me as a joke, if you like — if you dare — but I am not one of your little friends.

I am the cause of your friends' nightmares.

Grimly, he stalked unseen back down to the dungeons. If Granger asked, he would tell her the truth: that this had been a fool's errand, that words mended nothing, that neither he nor Neville Longbottom had anything to gain by ventilating old sins and old wounds. And he would tell her —

Snape stopped at the bottom of the stairs. The corridor wasn't empty. For once, it wasn't one of the irritating Gryffindors hanging about outside his door wearing expressions so studiedly nonchalant they were as good as holding up a sign saying Ask me what I'm doing.

It was Luna Lovegood. She was dressed in her usual absurd fashion: head-to-toe in shades of pale blue, from the ribbons braided in her fair hair to the boots on her feet. Her shirt was blue, her trousers were blue, and every one of the dozen pockets adorning each of them was a different shade of blue. There was even a blue feather woven through the links of the strange assembly of junk she wore as a necklace.

Snape moved soundlessly closer, and cleared his throat.

"Oh, hello," she said guilelessly. "I was hoping someone could let me in to the Potions classroom. We've got rather a problem with Flesh-Eating Slugs, you see. They seem to be developing a tolerance for the usual repellent."

Snape paused. That would be a problem, indeed, because such a resistance could spread rapidly within a population until in a few generation the Flesh-Eating Slug Repellent would be all but useless. It was also, however, exceedingly unlikely. He studied Luna, trying to determine whether she was lying or deluded — far from the first time he'd found himself confronting that dilemma.

He was no more successful on this occasion than on any other. Luna Lovegood was impenetrable. Either quite, quite mad, or the best and most consistent liar I have ever met. And he had met more than his share of liars. Even Legilimency failed against her — and he couldn't tell if it was because her mind was genuinely impossibly clouded with fictions, or because she was a particularly talented Occlumens.

"Come with me," he said at last, and led the way to the Potions classroom. The door-wards still recognised him, although for a few days after he'd taught Rowland to brew Cinderjuice, he'd wondered if Hermione Granger was going to change them. Once Luna had followed him inside, Snape closed and locked the door, and shrugged off the Invisibility Cloak.

She smiled, seeming completely unperturbed to see him appear from thin air. Perhaps she was used to Potter doing it. Or perhaps it's just far less startling than whatever it is that goes on in her mind. "Hello, sir," she said in her odd, soft voice. "It's good to see you."

Snape regarded her with narrowed eyes. Improbable as it was, he could detect nothing but sincerity in her voice or her expression. He inclined his head. "Madam Lovegood."

"Oh, do call me Luna," she said. "And I'll call you Severus. That makes sense, doesn't it? Since we're colleagues, now. And you're helping me with my slug problem."

"I would prefer —"

"Because you're not a Professor, any more, are you? And I can't see myself calling you 'Mr Snape'." She paused. "Or you answering to it, for that matter. Can you?"

"No," Snape allowed stiffly. He'd allowed himself to forget the way conversing with Luna Lovegood was like fighting fog: expending a great deal of effort to find oneself just as lost and blind as before. The only logical thing to do is to take the path of least resistance until she goes away. He cleared his throat. "So. The Flesh-Eating Slugs."

"Oh, yes," she said brightly. "Thank you for reminding me. Hagrid went to Knockturn Alley for a new batch of repellent, but it doesn't seem very effective. They're back within a few days, whereas usually it keeps them off for weeks." She produced a small jar from one of her pockets. "So I was hoping to test it, because if the standard repellent is starting to become ineffective, I have to alert the Ministry at once." She offered him the jar. "And if, as is much more likely, it's part of a plot to corner the market on cabbage by watering down Flesh-Eating Slug Repellent, I have to alert the Ministry at once. Unless they're behind it, but I don't think they would be, not with Kingsley in charge."

Snape took the jar, considering and discarding a dozen different responses, from a mild More likely still an attempt by the vendor to increase his profit to a blistering Madam Lovegood, do you ever hear yourself speaking and wonder 'who is that lunatic'? "Indeed," he said at last. "It will take me about an hour. If you'd like to return then —"

"Oh, I don't mind waiting." Luna hoisted herself up to sit on one of the students' benches. "We have a lot of catching up to do, after all."

Snape closed his eyes for a second. If the curse had started after these children returned to Hogwarts instead of before, I would find Granger's theory far more plausible.

Fifteen more minutes of Luna Lovegood, and he would quite possibly lose the will to live.

"I will require quiet, to concentrate," he said repressively, summoning the ingredients he would need and catching them, one by one, as they flew across the room to him.

"I'm not very loud," she said with a smile.

Fighting fog. Sighing, he summoned a cauldron across the room and poured the contents of Luna's jar into it. A tap of his wand started it heating. Once it was warm, the addition of distilled —

"This is the part where you ask me how I've been," Luna said.

Snape gritted his teeth. "This will take longer if you interrupt my focus."

"I don't mind, I've got all evening."

Merlin's beard. "How," he asked acidly, "have you been?"

"Really well, thanks. I was quite sad for a while, when Neville and I broke up, but we had a lovely time while it lasted, and I'll always be glad of that." She paused for a moment, but just as Snape had begun to hope she was finished, she drew another breath. "And I have a nice new friend, well, pen-pal really, we haven't met — he's been travelling in the South Pacific. Rolf Scamander, he has an interesting new theory about the Dukuwaqa." She paused again, and again, just as Snape was concluding with relief she would now be quiet, his hopes were dashed. "How have you been?"

"Longing for peace and quiet," he said meaningfully.

"Yes, it can get rather busy during the school year, can't it? But it will be Christmas soon, that will be nice. Do you have plans?"

Snape gave her an incredulous stare.

"Because if you don't, you're welcome to spend it with Daddy and me. Should you be stirring that quite so vigorously?"

No, he should not. Snape took a deep breath and composed himself, quietened his mind and dismissed his emotions — even the very-well justified one of extreme irritation. He had survived years of Flitwick's anecdotes, Dumbledore's heavy-handed moral lessons, Minerva's occasional explosions of Scottish expletives, and Charity's cheerful chatter. He could endure an hour of Luna Lovegood's ludicrous lunacy. "Thank you for the invitation, but I must decline."

"Let me know if you change your mind," she said calmly. "Or just turn up, if you want. We're easy to find — it's the same address as letters to the editor."

Despite himself, Snape was compelled to ask, "Isn't that inconvenient?"

"Dreadfully," Luna agreed. "And whenever Daddy publishes something controversial, it's very messy, too. But good for the garden."

If I'd had the remotest inclination to accept her invitation, the idea of a garden full of owl droppings would have put paid to it. Steam rising from the cauldron meant it was time to add the distilled Horklump juice, and he did so.

"It's your turn," Luna said. "To ask a question."

"I just did," Snape pointed out, watching for the colour change which would indicate the right moment to drop in the Adder's Fork.

"Oh, so you did! Alright. My turn, then. Don't you find it gloomy, spending all your time in the dungeons? I would."

"I find it quiet," Snape bit out. "Which I prefer." There was an expectant silence, and he ruthlessly suppressed a sigh. A question. He dropped in the Adder's Fork, and asked, "How is your father?"

"Oh, very well. We have ever so many more readers for The Quibbler now, since the War, so he's very happy. Lots of people wanting to write for us, too. He complains that he spends more time writing letters to writers than he does writing for the newspaper, but I think he likes it, really. Do you miss teaching?"

"No," Snape said coldly. "Nor do I miss students." One more widdershins stir, and then the essence of comfrey.

"I don't think I will, either," Luna said. "I mean, I quite like some of the students, but there are an awful lot of them, aren't there? It's exhausting. I think I'd like teaching much better if there were … twenty eight."

Snape paused, hand poised above the cauldron with the vial of comfrey. It's really better not to ask. "Have you suggested that to Minerva?"

Luna laughed softly. "Oh, I know it's silly. I just mean, teaching someone something is a wonderful thing, but I'd be much better at it if I could just teach them one or two at a time."

He added the comfrey and waited. "I would think that your primary duty in your current position is to ensure none of your charges is gored, trampled, slashed, burnt or eaten by one of Hagrid's pets."

Luna nodded. "There's that, of course. I think that Hagrid just doesn't understand that other people are a bit more fragile than he is."

"Quite a bit more fragile." He selected a silver spoon and dipped it in the mixture. The way the liquid shivered on the spoon's bowl told him everything he needed to know, but to be absolutely certain, he dropped a single Shrivelfig leaf onto it. It floated flawlessly, not a single drop of liquid adhering to the leaf. "You see? The Repellent has been diluted with onion juice, attenuating its efficacy."

Luna hopped down from her perch on the bench and came closer, peering at the spoon. "That's truly remarkable, Severus. And such a relief, too. Rampaging Flesh-Eating Slugs would be very hard to conceal from Muggles."

"Particularly once they began to gnaw on those Muggles' feet," Snape said. He vanished the contents of the cauldron and gathered up the ingredients to return them to their place.

"It's a shame it would be unethical to buy cabbage futures before telling the Ministry," Luna said with a sigh, helping him. "I could finance an expedition to South America quite easily that way."

"Or the South Pacific," Snape suggested dryly. "To discuss that interesting theory about the Dukuwaqa face-to-face."

Luna looked up at him with a dreamy smile. "I knew you were listening, really." Setting the jar she held on the shelf, she patted his arm just as if it had never held the Dark Mark at all. "See how much fun talking to people can be? Now you have something to tease me about for ages."

Snape raised his eyebrows. "And what benefit have you gained?"

Her smile changed slightly and her pale eyes acquired a mischievous glint. "The pleasure of knowing you'll lie awake wondering just what the answer to that question is, of course." She half-skipped to the door, which he unlocked with a wave of his hand, and opened it. On the threshold, she turned back. "Good night, Severus. Don't forget Christmas. I'll owl Daddy to lay an extra place."

"I said —"

Too late. She was gone, closing the door behind her.

Snape pinched the bridge of his nose, an awful suspicion beginning to grow. I very much fear I am fated …

To spend Christmas with the Lovegoods.

.

.

.

Author's note: the whole business with testing the Flesh-Eating Slug Repellent is completely made up by me. Flesh-Eating Slugs, and their Repellent, however, belong to JK Rowling. There's no canon on when Neville and Luna broke up, nor on how and when Luna met Rolf, so I made it up!