The afternoon passed slowly. Severus found himself somewhat abstracted in mind, thinking alternately about the possibilities of coconut ingredients and what he planned to show Lupin. At dinner they did not sit together, but somehow it was clear they were both aware of the evening's appointment. Lupin seemed quiet and thoughtful, and more than once glanced down the table, as if to check that Severus was still there. Severus, as usual, excused himself as soon as he had finished eating, and went back down to the dungeons to set things up for the Wolfsbane.
As he levitated equipment out of cupboards, he couldn't help casting a glance at the small, locked cabinet where he kept his restricted ingredients. Belladonna. Opium poppy. Digitalis. Coca. Hemlock. All in tiny, sealed vials or boxes. All fabulously expensive. All beautifully intoxicating, in the right potions. He just wanted to sleep, after all. If he restricted himself merely to –
He closed his eyes and breathed slowly. No. Not necessary. This would pass, his body would sleep when it was ready. He didn't need that stuff any more.
When Lupin arrived just after eight, Severus was sitting calmly at his desk, marking essays. He stood up. 'If you sit there,' he said without any further greeting, indicating the nearest worktable, 'we can perhaps go through some of the theory first so what I show you makes a little more sense.'
'That sounds like an excellent idea,' Lupin said, seating himself at the long worktable on which Severus had already placed Warts, Weathers and Worries, as well as a sheaf of parchment containing his own workings. Now he went over with a blank piece of parchment and a quill, then sat down across the corner from Lupin.
'You might remember from Slughorn's lessons,' he said, 'that we tend to represent the structure of potions most simply as a diamond shape.'
He sketched a neat rhombus on his parchment and drew three horizontal lines across it.
'The base or foundation of the potion is usually some type of water or oil. Glacial water, in the case of the Wolfsbane. Then the super-foundational layer' – he indicated with his quill the next level up – 'stabilises the base and tends to determine the longevity of the potion. This might consist of just one ingredient, or anything up to five or six. Then the layers from the middle to the apex tend to be more varied – the active ingredient of the potion might be at the top, or somewhere lower down. Monkshood is just below the apex here, and the acorn is at the top, it's that which catalyzes the whole thing. Does that make sense?'
Lupin nodded. 'Yes, that sounds familiar enough.'
'This diagram represents the finished potion, however,' Severus said, 'not the process of brewing it. Things would be very simple if one simply added ingredients from the base up, and there are one or two potions where this is the case. But mostly the process to reach this point is a matter of working out how to bind the ingredients together, and in what order, to make them interact the way you want. And then you can change those interactions in so many ways, as you know, through heating, or stirring, or chopping them up, or changing the quantities or the sequence of the ingredients, and so on.
'So designing a potion, or improving it, involves a sort of negotiation between the finished structure of the potion' – he pointed at his diagram – 'and the logistics of actually brewing it' – he laid a hand on the book containing the Wolfsbane formula – 'which really means negotiating with your ingredients, trying to get the most out of them, or seeing what they will tolerate before they become ineffective.'
He was aware that Lupin was sitting very still, listening to him. He was aware, too, that it felt rather nice to be able to show off his expertise to someone who actually wanted to hear it. This was what mastery meant.
'When it comes to other people's potions,' he went on, 'unless they're willing to share their research with you, you obviously have to work out the structure of the finished potion before you can set about trying to improve it. Sometimes it can be a bit speculative. Some ingredients are obviously bases, but many could go in almost any level of a potion.
'With the Wolfsbane' – he lifted the top sheet of parchment from the pile and passed Lupin his heavily annotated and crossed-out diagram – 'this is how it's structured, or, well, I'm about ninety per cent sure. As I said, it's not designed very well. This lamination technique is too fiddly for a potion that's meant to be brewable at home. Most people wouldn't be able to get this right, or not reliably, anyway. So it needs improvements.'
'I'm very reassured that you think it's so hard,' Lupin said, smiling. 'I was getting frustrated at my lack of skill.'
'How long had you been making it yourself?'
'Just over a year.'
'Then you clearly have a certain competence.' He tried to ignore Lupin's grin at this half-praise. 'Anyway, the theory I've just told you is taught from the sixth year, and students are examined on designing very simple potions at NEWT level. I've argued that improving existing potions should be on the syllabus too, but the Ministry doesn't agree. So as you said, you wouldn't have learned this next part at school.'
'But you did, presumably?' Lupin said. 'I mean, you must have studied a lot of extra-curricular stuff when you were a student.'
Severus stared at him. He couldn't mean –
No, he decided, looking at Lupin's mild face, that wasn't what he meant. In the end he said, 'Yes, I read a lot. Slughorn let me try things out in the evenings sometimes. And …' He inhaled, hesitated, then spoke again. 'Well, as you know, I didn't do an apprenticeship after I left, so … But I had most of the knowledge I needed. I made up for the gaps later on, after the – when I became a teacher.'
There was a pause. Severus kept his eyes down on the parchment so he couldn't see Lupin's expression. He didn't want to know whether it was compassion or contempt.
Eventually he said, 'Anyway, so, improving a potion requires an understanding of its deep structure, how the ingredients bind together. In the case of the Wolfsbane, it seems Gilchrist has been somewhat lazy – he has tried to stretch the longevity to the three days you need by adding woody nightshade, but ignored the fact that this interacts badly with the poppyseed. This is why it makes you sick. And the lamination is designed to protect the monkshood so it can develop its potency more slowly, which means you can brew it all in one cauldron, but actually this makes it very difficult for an amateur.'
'I thought Gilchrist was one of the most respected potions masters in the country,' Lupin said.
'He is.'
'So why –'
'Because the discovery itself probably took a great deal of time. He can register the invention and the lamination technique, make some money, and be credited with improving the lives of werewolves all over the world. To make the potion better, as you can see, is the tedious part. I imagine he preferred to leave it to others. Anyway, I will show you.'
Severus rose from his seat and Lupin followed him over to the next worktable, on which he had arranged eight racks of vials, next to a row of six simmering cauldrons. The big ledger in which he had been recording his work, and Lupin's reactions to the potion, was lying open at the end of the table.
'Here is how it works,' Severus said. 'I've been trying rosewater to slow the development of the potion, so the timing of the lamination isn't so crucial. I've mixed twelve different concentrations and tried each one – each rack here contains each of those twelve concentrations – and then for each rack I've varied it again in terms of the quantity I've added, three different amounts' – he waved at the first three racks – 'and then different temperatures, five at present. After that I'll look at how quickly to add the rosewater, all in one go or gradually, or in several stages. And then these cauldrons are brewing a new batch to the point where I add the rosewater. That'll be the weekend's research.'
Lupin was looking carefully at the ledger, and each of the racks and cauldrons. 'I can't actually tell the difference between any of them,' he said. 'What you're doing must be very subtle.'
'It is. It will make a difference at a single moment of the brewing process, and that's all. But it will already be a big improvement if I can get it right. I have also, on instinct really, moved the poppyseed slightly earlier in the formula, to try and reduce the nauseating effect of the woody nightshade. That made theoretical sense, and it seems to have worked all right. And then, as you know, I'm looking for a different base, which might ultimately mean redesigning the potion from scratch.
'So those are the three different methods.' Severus held up a hand and counted them off on his long, pale fingers. 'One, intensive testing of minute variations in the formula. Two, changing something on a gut instinct and seeing what happens. And three, wholesale redesign. If the last one doesn't work, at least we should end up with an improved, more workable version of the original.'
He returned to his desk and sat down behind it, leaving Lupin at the worktable. He hadn't spoken so much in one evening for a long time, and it was very draining, especially when he was already so tired. Lupin hadn't even been there a whole hour, but already what Severus wanted was for him to say thank you and go away, to leave him in peace.
Lupin looked at him, seeming to notice his change in mood, but did not leave. Instead he said, 'Could I look through your ledger, or is it private?'
'If you must,' Severus said without looking up.
As Lupin pulled a stool up to the worktable and began to turn the large pages, Severus found his half-completed stock order from earlier in the day and continued to fill it in, to send to Hogsmeade in the morning. He added the various kinds of coconut ingredients he wanted – large amounts, hang the expense. He was starting from scratch, after all.
The minutes passed in almost complete silence. Lupin didn't speak even when Severus came over to the worktable again to check the six cauldrons, taking a small spoonful of each and drizzling it out to check the consistency. He could feel Lupin watching what he was doing, but it seemed the werewolf was unusually respectful of quiet, even more so than Dumbledore, who had a tendency to fill gaps in the conversation.
The silence was broken, however, when Lupin, now reading the ledger again, gave a little chuckle.
Before he could stop himself Severus said, 'What is it? Have you found a spelling mistake?'
'No, I'm just amused by your description of me as slightly disinhibited,' Lupin replied with a smile.
'Ah.' Severus cursed inwardly: he'd forgotten about that little note when he'd given Lupin permission to read the ledger. But perhaps it was a good opportunity to ask. 'Would you consider that an accurate observation? Your mood seems to change slightly just after you drink it.'
Lupin's smile became wry. 'That seems more or less accurate, yes. Usually I drink it alone, of course, so there hasn't been anyone there to notice.'
He came over and half-sat, half-leaned on the nearest worktable. There were several large holes in the sleeve of his jumper, which Severus pretended not to see. 'This is clearly a very time-consuming project for you, Severus. I'm really very – very grateful you're giving it so much attention. I wanted to ask if you need any help with it. I'm happy to give you what free time I have if it would be of any use.' The ghost of a smile appeared on his face. 'Except at the full moon, obviously.'
Severus considered. 'To be honest, the biggest obstacle is that it can't be tested often enough. You are the only person here who can drink it, and only one dose, once a month – and it absolutely must be right when you do, or the consequences are pretty serious. Normally I'd test a potion on myself as I went along, and if it went slightly wrong it wouldn't matter too much. But that's just the nature of the situation. What progress I can make given those restrictions, I can cover in my own time.'
'Fair enough,' Lupin said. 'Well, the offer's there, my time is yours if you want it. Also –' He hesitated, suddenly seeming a little uncomfortable, then spoke again. 'I wanted to apologise about what I said a while ago, when I said you hadn't changed.'
'Apologise? Why?'
'Well, it was a joke, but I realised afterwards it wasn't in very good taste, given all the reasons for … And I didn't want you to imagine that might really be what I think – because you have changed, a lot, or at least from what I know of you.'
'So have you, I think.' He didn't know what had made him say it.
But Lupin did not seem offended. 'Yes, I think I have,' he agreed. 'We've both had to adapt to – some bad circumstances.'
Severus wasn't sure how to respond. Talking about the past could lead them into dangerous territory. If they discussed their schooldays they would have to recall the bitter hostilities that existed between Severus and Lupin's friends; only a few years later, Severus had passed onto Voldemort the prophecy that had led to James and Lily Potter being murdered – did Lupin even realise to what extent this had been Severus's fault? – and now there was Sirius Black. None of this seemed safe to talk about.
'Well, anyway,' Lupin said, 'I'll leave you in peace. Thank you for the tutelage, you are very good at explaining things. Good night.'
He was halfway to the door before Severus said, 'Lupin?'
The werewolf turned.
There was a pause. What Severus wanted to ask was why – why Lupin was being so friendly, why he was going out of his way to spend time in a dark dungeon with a former Death Eater, why he was making jokes, making personal remarks, offering up his free time. But in the end all he said was, 'What is the date of the next full moon?'
'Oh,' Lupin said. Clearly he had sensed a more serious question. 'The twenty-eighth.'
Severus nodded. 'Good night.'
Lupin looked at him for a moment, then turned and left the dungeon.
A/N: Sorry for the delay in posting this– university term started again, and I ran out of backlogged chapters! Progress will likely be slower now, but I'll try not to lose too much momentum.
