Gray and wet as it was outside, it could have been a sunny day once those cabinets were opened. Tray after tray blazed as they were brought out.

“Well,” Crane remarked at last, when he’d looked it all over. “Well. Ten keys. Have you ever encountered a lock that needed so many, Briar?”

The boy shook his head emphatically, speechless. Hope was so thick in his throat that it half choked him.

“Now you have. A disease is the most complex lock there is,” said Crane. “We have more keys to find, so if we might begin?” He looked at his staff. They disappeared into the outer room, eager to get started.

“What are you working on?” asked Rosethorn, holding out a thin hand.

Daja jumped, startled—she had thought Rosethorn was asleep. When the woman’s fingers twitched, demanding, she blushed and passed her work over. She had been trying to shape copper wire to combine the signs for health and protection. She’d wanted to put it in a brass circle and hang it above the bed. For some reason, though, when she added her magic, the metal twisted, jumping out of the pattern.

Rosethorn eyed the design. “Interesting. It might work better as a plant. If Briar built a trellis in this shape, we could grow ivy on it. You know why I hate plagues?”

The girl hesitated, confused by the abrupt change of subject. That was the fever, she realized. It made Rosethorn’s mind skip about. “Why?” Daja asked.

“Most disasters are fast, and big. You can see everyone else’s life got overturned when yours did. Houses are smashed, livestock’s dead. But plagues isolate people. They shut themselves inside while disease takes a life at a time, day after day. It adds up. Whole cities break under the load of what was lost. People stop trusting each other, because you don’t know who’s sick.”

“How did you get in with Crane?” Daja inquired, curious. “Picking apart diseases?”

“It was a game,” Rosethorn confessed. “I was sent here to complete my novitiate. Crane was a novice too. We were the best with plants. A lady was visiting one day, and I worked out the ingredients in her perfume before Crane did. Except he wasn’t Crane, then, he was just Isas, like I was Niva.” Her eyelids started to droop, a sign she was tiring. Daja poured out a cup of willowbark tea and gave it to her. Rosethorn sipped, made a face, and continued. “We just went on from there. We’d make scents and give the other a day to figure out what was used and the amount. Then we worked out the ingredients in stews, and the dyes for the complex weavings that came in from Aliput. Then medicines—and then diseases. The temple sent us both to Lightsbridge for three years. I hated it, all those books and dead chemicals, powders, nothing alive. And they made so much of him as a count’s son….” She finished her tea and eased herself back. “So arrogant. So good at what he does. He’s been a burr between my toes for years.” She pulled the blanket up over her shoulders.

Daja set the empty cup in the bucket of things to be washed in boiling water and put the lamp behind a screen. She was about to try her work again when Rosethorn muttered something.

“What is it?” asked Daja. “Or are you walking in dreams again?”

“My boy. You three girls—look after Briar. When I’m gone.”

Sandry and Tris would have argued passionately, refusing to admit there was a chance that Rosethorn might die. Daja was a Trader: they held it was mad to argue when the sick thought that Death approached. Denials only told Death here was someone who would be missed, Death’s favorite kind of victim.

Daja did not protest. “We’ll look after him forever,” she promised.

“And tell him to mind my garden,” whispered Rosethorn. She went to sleep.

Daja went back to her chair, but she couldn’t work. Her eyes had gone blurry.

So many keys were found that day that Briar and Tris fumbled their way home, the afterimages of lightsprays still floating in their eyes. They were giddy with hope when they reached Discipline, eager to tell everyone what they had seen.

Their high spirits evaporated when they visited Rosethorn. She didn’t know them. She was flushed with fever, and hallucinating. They heard her plead with her father to go to the harvest dance, and in a younger voice scold someone for tracking across her rows of seedlings.

Sandry, in the chair by the bed, smiled woefully at them. A piece of embroidery lay on her lap. When Tris picked it up, not wanting to look at the woman whose hands stirred restlessly on her blanket, she saw the beginnings of a needlework portrait of Rosethorn. She dropped it as if it were a hot coal.

More keys were found in the morning. When Acacia announced lunch, Crane gathered his staff together.

“Begin to pack the sample boxes in crates,” he ordered. “If things go well, we shall only need to burn their contents, then melt down the boxes. Distill no more blue pox samples for the present time. The five jars we have, as well as what is already in the trays, should suffice.”

“We’re done?” someone asked. Two more began to applaud.

Crane shook his head. “As far as I can tell, we have found all the keys to the illness. Now we formulate a cure. We have available a number of ways to cancel individual keys, which are different parts of the disease. These ways do not all work together. A bad combination of cancelers will kill a patient as easily as the blue pox. Also, different people react in different ways. Now we must devise the canceler blends that will treat the largest number of the sick.”