“They develop resistance to each disease. But the newer the disease, the more people it kills with each resurgence. And some of them mutate, so that people who lived through one iteration have no defense, or little defense, against its successor.”

“I hate to be offensive, but this makes me wonder what’s hiding there. What you don’t want me to see.”

“What’s hiding there is death, and what I don’t want you to see is the inside of your coffin lid.”

“So you keep me out of Janefold with a threat of plagues. What will be the excuse the next time you want me not to visit a place? Earthquakes? Really bad weather? Ill-behaved children?”

“This is how the world works,” said Ram Odin. “It happened on Earth. There were a couple of places that spawned plagues that covered the world, because trade routes connected them to everybody. But there were other places that were cut off. The Americas didn’t spawn a lot of diseases because population density never got that high, and because there weren’t a lot of primates to incubate diseases that would be particularly apt to kill humans. When people from Eurasia landed there, those worldwide diseases, in combination, had a killoff of about ninety percent of the locals.”

“I read about that.”

“Africa was the opposite. It was isolated, too—not a lot of trade, because traders had to cross oceans and deserts. Sick people tended to die before they could spread the diseases to the rest of the world. But when Europeans got there, if they went ashore for a week they simply didn’t come back. If they went ashore for a day, they came back to their ship and infected everybody else and some ships were found drifting, with a one hundred percent killoff.”

“And you’re saying the Wall has protected the rest of the world from Janefold. If I visit there—”

“It would be miraculous if you didn’t catch something incurable and highly contagious. And here’s the problem. You can’t go back in time and change it because you’ll have the disease in you already.”

“I also have the facemask.”

“So you’ll have much keener awareness of your symptoms and be able to track the progress of your disease quite clearly, as you die.”

“The facemask doesn’t help keep me healthy?”

“It helps keep you robust,” said Ram Odin. “It doesn’t filter out diseases that your immune system can’t cope with, because it can only detect disease agents from Earthborn biology if your body senses them.”

“Yet people live there.”