There was something cold about Snape’s room that had nothing to do with the dungeons.
To Cael, sitting at a long stone table during the second class of his second week of October and staring at a pristine copy of his first-year Potions textbook open in front of him, there was an *intentional* coldness here.
Snape ran his classroom much the same way many men ran kitchens: with the meticulousness of someone who knew exactly how the end product was supposed to be, and the result of whom was the oppressive precision that spoke before cooking started to begin that the cooking would be done correctly.
Heat emanated from the cauldrons.
It was intended to.
Only from the cauldrons.
The stone walls and floor and long, narrow windows above them seemed to agree in this assessment.
Cael liked it.
This was apparently an odd stance.
Ron, to his left, despised Potions, both generally and in practice.
Hermione, who was seated two rows in front of him and whose hand had barely stopped moving since she’d sat down, loved Potions so much she’d brought a notebook with her in order to record everything Snape would teach them today, because that’s the type of person she was.
Neville, across the room at the moment and being watched by Snape in the way he watched Neville — standing over his shoulder at a distance of roughly three feet and not moving — had lost almost a year of his life to this classroom.
Harry, who was sitting a little further up the row from Ron and who possessed a personal grudge with Snape that went back far longer than Cael’s time in this universe.
But Cael liked it.
The precision of the process fascinated him.
He also enjoyed the process of brewing itself.
*Crush, do not chop*, *chop, do not crush*, and *anti-clockwise three turns then count to twelve*.
Then there were the recipes themselves, written as if the potion brewing process were akin to putting together an incredibly sophisticated machine and testing it the first time with an inevitable malfunction.
There wasn’t supposed to be improvisation in Potions until you knew enough to justify it through the understanding of the system.
That understanding had taken years in some places.
Cael understood, instinctively, that he wouldn’t be improvising this term.
He was planning to be able to do so eventually.
For now, however, he would do as the book told him.
Today’s potion was a Cooling Draught.
Snape had explained the brewing process with a voice that implied he expected to be ignored and proceeded accordingly.
He’d drawn a graph on the blackboard of what the temperature change would be, when each ingredient was to be added, and the exact five-second window the mint must be added or the whole endeavour would scorch the bottom of the cauldron and yield some sort of potion that was apparently about as helpful as cold soup.
Afterward, he’d simply said, “Begin,” and walked away.
Cael followed his directions.
The beginning had gone well.
The scent of the ingredients was pleasant: fennel, something acidic like a citrus fruit peel, and a base-note of camphor.
The cauldron itself behaved in accordance with his expectations: when it was supposed to go a certain colour, it went that certain colour.
His partner today was a sixth-year boy from another House, a Hufflepuff named Thad who contributed to the brew by standing beside him and telling him, *Yeah, no, that looks good.* Thad was useful.
He kept things on track.
He counted the time Cael needed, he had not once made reference to Cael falling from his broomstick.
It had become clear to Cael relatively quickly that this was becoming a valuable commodity in his life.
Everything had gone according to plan until the forty-fifth minute, when Cael saw the convection.
It was subtle.
Just a thin swirl in the potion’s surface, slightly off-centre, reminiscent of a thumbprint in thick, creamy liquid.
Cael stared at it for several seconds, wondering what on earth it might be.
The book had not mentioned convection.
It hadn’t treated the cooling potion as anything more than a stationary object.
However, the previous night, Cael had read several sections ahead from *Advanced Potion-Making* reference that Hermione had loaned him (Hermione had walked up to him in the library, handed him her copy, then walked away) and found that, due to an unstable temperature gradient in the cooling process, the potion would behave this way and require a stabilizing charm on the surface in order to return it to its stable phase.
He took out his wand.
He didn’t think about his magic.
This would turn out to be the problem, in retrospect — he had been doing well for forty-five minutes, working with a non-magical process, and the wand had been in the pocket of his robes.
It was as automatic to use the stabilizing charm as taking a pinch of pepper from the shaker.
Whispering the spell and waving his wand just the slightest amount to apply the necessary force was done in the split second before he heard: The swirl got larger.
It became a whirlpool.
The whirlpool turned into a larger whirlpool.
The whirlpool then created a brief upwelling of steam in the middle of the cauldron.
It clouded over.
What had been a glassy-green potion was now darkly bruised in color.
Cael set his wand precisely back down on the bench.
“Hey, mate,” said Thad.
“I know.” “Uh…
” “I know.” He already had the process several steps in advance.
*Inverted stabilizing charm.
The opposite of stabilizing is destabilizing.
The opposite of stabilizing on the surface is heating on the surface.
Twice as powerful and twice as long in application.
The potion is destroyed.* It took him seconds to pull the notebook out from beneath the desk.
He grabbed the quill he carried specifically for such occasions in the side pocket of his bag, and wrote, as the cauldron clouded calmly in front of him: *Inverted stabilizing charm: heating, surface applied.
Mechanics: opposite vector, double intensity.
Cauldron irreparable.* He stared at it.
He drew a line under the phrase “opposite vector, double intensity”.
Then he added: *file for testing* A large shadow blocked the bench.
Cael did not immediately look up.
He wrote the last few words of the line.
He set the quill back down and, with an air of inevitability, looked up.
Snape stood at the other end of the bench, looking not at Cael, or at Thad, or at the two girls a bench over or the three benches ahead where Ron was looking at him with increasing confusion, or even at the ruined potion.
Instead, he was reading.
Reading Cael’s notebook.
Cael let him read.
The reading process took about eight seconds.
They were eight very long seconds.
The entire row around them was growing very quiet in the way they did prior to identifying events.
Snape said nothing about the potion.
He did not, in fact, glance at the potion.
Instead, he looked at Cael and gave him a look Cael had seen only once before.
The look he had given him in the hallway three weeks ago when Cael had tried to drag a screaming Neville back into class.
It was not a particularly long look, but neither was it warm or cold.
Cael had the impression he was giving him the long look of a man who had read something carefully and decided what he wanted to do with the information.
“O,” Cael, for about half-a-second, had no idea what he was talking about.
“Yes sir?” “For the class.
An O.” Cael was stunned.
“Yes sir, the cauldron is —” “I am aware, Mr.
Mourne.
Of the state of your cauldron.
Your cauldron is entirely irrelevant.
You’ve been graded an O for your documentation.” “…” “Do not,” Snape.
“argue with me when I give you an O.
People complain when I give them a U.
They haven’t yet had the imagination to argue about an O.” Snape moved past them.
He did not stop anywhere else in the room.
Thad, who had been holding his breath in the way a man holds his breath when the announcement of an evacuation begins, breathed again loudly.
The two girls a bench away from them exchanged a whisper.
Ron three benches away mouthed *what?* Cael didn’t know either.
He cleaned up the mess.
He put his notebook away.
He ate dinner.
After dinner, he went to the library and started looking up exactly how much of an O was too much, because he was almost certain there weren’t very many O’s issued by Snape.
He read three sources.
He read four.
On the fifth, he figured it out: there had only been fifteen documented O’s in the grading registry for all the years Snape had been teaching any subject at Hogwarts in the past ten years.
He sat in the library, staring at the registry.
He thought.
He thought, in particular, about the contents of his notebook.
The entry he’d scribbled in there in less than five seconds had been both extremely technical and entirely accurate.
It’d identified the problem, the cause, and the solution and had noted the failure of the stabilizing charm for future use.
In essence, his notebook entry had not focused on the failure of his cauldron as an individual, but had rather treated it as a data point in an ongoing experiment he conducted on the process as a whole.
Snape had recognized the difference.
Until this point, Cael had been entirely confident he knew what was going on with him at this school.
He had, apparently, been mistaken.
Snape, who had not spoken to him in any extended capacity, had seen him clearer in eight seconds than anyone else at this school had seen him in the three weeks since his arrival.
He closed the grading register.
There were two new things Cael had to put in his notebook.
The first was the inverted stabilizing charm, because he had written the spell down in case he had to reproduce it.
The second was Snape’s approach: *Snape teaches systems, not results*.
Cael underlined this.
He spent a moment watching Madame Pince make her rounds of the third-floor stacks, and then he added: *This will matter.* He didn’t quite know why at the time.
But he was correct.