“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.”

“If they make it through childhood, then they tend to have lives of normal length. Childhood is when disease weeds out the weak and selects for those who adapt well, whose bodies resist. The longer the disease has been around, the more children live through it. But there are some diseases that are less than a thousand years old, and those are still taking a lot of children. So at birth, half the life expectancy. But if you live to adulthood, then the survivors have normal lives.”

“Do they have larger families?”

“Some cultures within Janefold do, some don’t. Some don’t bond with their children until they’re older. Some break their hearts loving all their children from the start. Some regions and tribes avoid large concentrations of people. Some keep their children isolated. Some deliberately allow their children to get exposed to everything—I suppose to end the suspense. Some villages, some tribes routinely burn down the houses of families who have a few key symptoms—open sores all over the body, bleeding from eyes, nostrils, and ears, blood in sneezes and coughs, that sort of thing.”

“Burn them down with the people inside.”

“That’s the point.”

“So you’re just protecting me.”

“If somebody comes at you with a knife, you can pop back in time and save yourself. If somebody comes at you with a sneeze, you have nowhere to run.”

“But I don’t breathe,” said Rigg. “The facemask does.”

“The facemask doesn’t have an Earthborn biology. It will pass the disease through to you without noticing it’s there.”

“You have to understand, Ram Odin. I’ve been lied to so much.”

“Not by me.”

“We only just met, and your lie-to-truth ratio is pretty high. Plus most of the expendables’ lies originated with you. Or they were invented in order to protect your secrets. What are you protecting in Janefold?”

“The future of the human race on Garden,” said Ram Odin. “By not letting that poisonous place kill you.”

“The future of the human race here no longer depends on me,” said Rigg. “You’re thinking of my other self, Noxon.”

“We don’t know how that mission will turn out. Rigg, please trust me on this one. There are no great secrets in Janefold, except death. Maybe because of systematic isolation, there are a few more languages. Some intriguing philosophies, a few death-worship religions, a lot of fatalism. One religion that for almost a thousand years was almost universal in Janefold, not because the doctrines were so convincing, but because the believers routinely risked their own lives to care for the sick and dying, and to bury the dead.”

“That made the religion more attractive?”

“It made the believers seem more sincere, and filled others with gratitude and admiration. Rigg, all the records are open to you. Explore this one from inside the ship and save your legwork for a healthier place.”

Because the facemask picked up subtle nuances he would normally have missed, Rigg could trust his judgment more than he used to, when it came to discerning whether people were telling him the truth. He became mostly convinced that Ram Odin meant what he was saying, whether it was true or not.

“So if we skip Janefold,” said Rigg, “where next?”

“Anywhere else. When I said this was the only one I’d resist your visiting, I meant it.”

“Singhfold,” said Rigg.

“An intriguing one. The only wallfold where the crater from the ship’s impact is the most level ground. Singhfold is mountainous, with lots of valleys and a huge range of cultures.”

“Are the individual tribes very small? That usually implies that the culture isn’t going to rise very high.”

“There is a broad, well-watered coastal plain where some pretty high civilizations have risen and fallen. But most of the people, most of the time, have lived in those isolated valleys. Shall we give it a go?”

“I reserve the right to come back to Janefold. To do it last.”

“Whenever you go there, Rigg,” said Ram Odin, “you’ll do it last.”

What Rigg thought was: I’ll go back in time, to when the colony in that wallfold was young, and so were the diseases that infest them. Because people who live in the constant immanence of sudden, miserable death by an invisible hand—it has to change them.

And if we ever have to protect ourselves against the people of Earth . . .

“Ram Odin,” said Rigg. “All this information about Janefold was available to the Odinfolders, right?”

“I kept a few secrets, but not that. Yes, they knew.”

“And the mice can move things remotely, through space and time. Things as small as DNA molecules.”

“Those are big molecules.”

“They’re still molecules,” said Rigg.

“That’s how Umbo was made. By genetic manipulation conducted remotely, by the mice.”

“So the mice that were boarding the Visitors’ ship, the ones that Umbo and Param warned the Visitors about—they could have gotten their diseases from Janefold.”

“You don’t know if a disease is virulent unless you test it,” said Ram Odin. “Janefold is by far the best disease laboratory in the world.”

Rigg chuckled at himself. “I wasn’t sure if Umbo and Param were right about the mice being sent to Earth to wipe out the human race. Where would they get such a disease? And I didn’t believe you, though I didn’t disbelieve you, either. About Janefold.”

“But combine the two doubts, and . . . certainty?” asked Ram Odin.

“Not certainty. But a major shift in my view, yes.”

“So you’ll stay away from Janefold. For real this time, not just an empty promise to placate me?”

“The mice got their species-wrecking plague from somewhere.”

“Oh, you might go farther,” said Ram Odin. “They probably enhanced it, and tested it in some of the villages.”

Rigg took that in for a moment.

“You did understand that the mice are not human. They have no more qualms about testing a disease on human subjects than we would have testing it on mice.”

“They got their sentience from us,” said Rigg.

“And for how many generations should that make them grateful and subservient? But I don’t know they did this. I’m only guessing from what I know about them. They did kill Param, though.”

“That was the Odinfolders’ idea, wasn’t it?”

“It might have been,” said Ram Odin. “But for a long time now, all Odinfolder decisions are based on data that is supplied to them . . .”

“By the mice,” said Rigg.

“So whether the mice decided for themselves, or provided shaped data to the Odinfolders so they reached the desired ­conclusion—”

“Nothing much happens in Odinfold unless it’s what the mice want,” said Rigg.