Aldith kept her half of the Codex in a hand so small and careful that Thomas needed a candle held close to read it, even at midday.
He found her in the corner of the schoolhouse she'd claimed for her own — not by anyone's grant, simply by the slow accumulation of jars and dried bundles and a stool that had migrated there over weeks until everyone understood it belonged to her now. She didn't look up when he came in, absorbed in transcribing something from a wax tablet crowded with her own shorthand.
"You've filled more pages than Wat and Elias combined," Thomas said.
"Wat mistrusts ink. Elias thinks in maps, not words. I think in symptoms, and there are a great many of those to write down before the summer fevers come again." She finally set the quill aside, flexing her cramped fingers. "I want to show you something, if you have a moment you're not pretending to have."
She turned the quire toward him. The pages were dense, organized in a way that had nothing to do with how Thomas would have arranged them — not by disease, but by what she called the shape of the sickness: fevers that came with a rash first, fevers that came with a cough first, fevers that killed within days against fevers that lingered for weeks and killed almost no one. Beside each entry she'd noted, in a small marginal hand, which of Thomas's remedies had worked, which hadn't, and — more than once — a flat, unflinching unknown, watch and record.
"You've organized it by presentation," he said, surprised into something close to admiration. "Not by cause."
"I don't know the cause of half of what I treat, whatever you've told me about small creatures too tiny to see. I know what I can observe with my own eyes at the bedside, and I've learned that a fever that starts in the throat behaves differently than one that starts in the gut, regardless of what invisible thing supposedly started it. I would rather build the book from what I can verify than from what I've simply been told to believe." She said it without apology, watching him for a reaction the way she'd watched everything since the night she'd been named. "Is that a problem for your Codex?"
"It's exactly the point of it." He turned another page, and stopped at an entry that made something in his chest go still — a careful description of fever with rose-colored spots, lethargy, a slow, wasting decline over weeks rather than days. Beside it, in her small hand: seen twice this winter in the lower parish, both survived, cause unknown, worth watching closely.
"You've seen this before."
"Twice. An old man near the mill, and a weaver's daughter. Both recovered, eventually, though the girl lost most of a season to it. Why?" She caught something in his face and set down what she was holding. "You know this sickness."
He did. He had read about it once, a lifetime and a world away, in the idle way a person reads about a danger that has nothing to do with them — a disease with a name he couldn't recall clearly enough now to trust, associated in his memory with crowded conditions and slow, dangerous fevers, the kind that could tear through a garrison or a besieged town in weeks. He had no certainty that it was the same illness. He had no way, here, to prove it either way. That was, he understood now, precisely the problem the Codex existed to solve.
"I don't know its name," he said honestly. "I know it's the kind of sickness that gets worse, not better, when people are crowded together — soldiers in a camp, a town under siege. If it comes back, and it comes back somewhere crowded, I want you watching for it before anyone else understands what they're looking at."
Aldith studied him for a long moment, and he could see her deciding, visibly, whether to press him on how he knew such a specific and useless-sounding fact. She chose, in the end, not to.
"Then I'll watch for it," she said simply, and made a new note in the margin, her small hand steady. "That's the whole use of writing it down, isn't it? So that the next time, someone doesn't have to already know the answer. They only have to have read the page."
Thomas left her to her work, the candle burning low behind her, and walked back out into the cold afternoon with the particular unsettled feeling that came from being handed a fragment of the future he couldn't yet do anything useful with. He thought of the plague years he half-remembered from old lessons, dates and death-tolls with no faces attached to them, and wondered, not for the first time, how much of what waited for this valley he was capable of preventing, and how much he would simply have to watch arrive, exactly as Aldith watched her fevers — recording, noting, unable to stop what he had already recognized.
He said nothing of it to Victoria that evening. It was not yet a danger. It was only, for now, a page in a book that hadn't needed it yet, and he told himself that was reason enough to let it wait.