“But no one knew any of this a hundred years ago,” Pierce said. “Even with modern science, it took decades to figure out that this was a type of malaria, or that it came from mosquitos and birds. See, the birds would get the disease, but they’d never get sick from it. They just carried it. They lived with it, no problem. And the kind of birds that usually got it always nested deep in the jungle, far away from where most people lived. The only people who ever caught the disease were tribal clans who lived far outside of towns and villages, closer to those bird colonies. Even for them, it was a rare thing. For some reason the infections only happened when the weather was unusually hot—maybe at high temperatures the disease lived a bit longer inside the mosquitos. Long enough for them to pass it to humans. Whatever the case, imagine how all of this looked to people who lived in bigger cities in the tropics, along the coasts, far away from the birds. Every few years, when a heat wave comes along, strange people come staggering out of the jungle, attacking and murdering whoever they catch. The infected were usually skin-and-bones by the time they emerged from the forest, after days of rarely sleeping or eating. They looked like corpses. Walking corpses. If you were around back then and witnessed something like that, would you have known any better?”

“I guess not,” Dani said.

“No one did. That same misunderstanding happened in every place that was afflicted, all over the world. There’s a telling detail: the local people never gave the disease a name, like black plague or spotted fever. They didn’t know it was a disease. Instead they named the victims, the apparent living carcasses that showed up on occasion to attack them. The Spanish settlers in Central America and the Caribbean called them los bailarines terribles: the terrible dancers. They lived in fear of them.”

Pierce glanced over his shoulder at the distant barn, where the men were visible as tiny, hurrying specks against the lit-up doorway.

“And that’s how it stayed,” Pierce said, “until around 1950, when scientists put it all together. Then the governments of each of these countries sent exterminator teams into the jungles, and wiped out the bird colonies entirely. It wasn’t hard to do; they nested in huge groups, and there were only so many sites. It might sound harsh, but it was the only way. And it worked. The disease vanished except for a passing occurrence here or there, in which case they just sent in more exterminators. Basically it was under control, and after a while no one thought about it anymore. Except for people who are paid to think about things like that. People like me.”