Rigg saw the stream before any of the others.
Loaf was an experienced soldier; Olivenko not so experienced, but not untrained, either; and Umbo had grown up in the village of Fall Ford, which was almost like living in the woods.
But only Rigg had tramped the high forests above the Upsheer Cliffs, trapping animals for their fur while the man he called Father taught him more than Rigg ever thought he would need to know. Rigg practically smelled water like an animal. Even before they crested the low grassy rise he knew that there would be a stream in the next crease between hills. He even knew it would be only a rill, with no trees; the ground here was too stony.
Rigg broke into a jog.
“Stop,” said the expendable they were calling Vadesh.
Rigg slowed. “Why? That’s water, and I’m thirsty.”
“We’re thirsty,” said Umbo.
“You cannot drink there,” said the expendable.
“Cannot? There’s some kind of danger?” asked Rigg.
“Or a law,” suggested Olivenko.
“You said you were leading us to water,” said Loaf, “and there it is.”
“That’s not the water I’m taking you to,” said Vadesh.
Only now did Rigg realize what he wasn’t seeing. It was his inborn gift that all the paths of the past were visible to him. Humans and animals all left traces behind them, paths in time. If they ever traveled through a particular place, Rigg could tell where they had gone. It was not something he saw with his eyes—his eyes could be closed or covered, or there could be walls or solid rock between him and a path, and he would still know where it was, and could figure out what kind of creature made it, and how long ago.
There had been no human traffic at this stream in ten thousand years. More tellingly, few animals had come there, and no large ones.
“It’s poisonous,” said Rigg.
“Is that a guess?” asked his sister, Param, “or do you know somehow?”
“Even animals don’t come here to drink,” said Rigg. “And no human for a long time.”
“How long?” asked Vadesh.
“Don’t you know?” asked Rigg.
“I’m curious about what you know,” said Vadesh. “I have not known a human who can do what you can do.”
“Nearly as long as since the beginning of human settlement on this world.” Rigg had a very clear idea of what paths that old were like, since he had just crossed through the Wall between his home wallfold and this one, by clinging to an animal that, in the original stream of time, had died in the holocaust of humans’ first coming to the planet Garden.
“That is off by only a little less than a thousand years,” said Vadesh.
“I said ‘nearly,’” answered Rigg.
“A thousand years this way or that,” said Param. “Close enough.”
Rigg still didn’t know Param well enough to tell if her sarcasm was friendly teasing or open scorn. “What kind of poison?” he asked Vadesh.
“A parasite,” said Vadesh. “It can live out its entire lifecycle in the stream feeding off the bodies of its siblings, ancestors, and descendants, until one of them eats it. But if a larger animal comes to drink, it attaches to the face and immediately sends tendrils into the brain.”
“It eats brains?” asked Umbo, intrigued.
“No,” said Vadesh. “It infiltrates them. It echoes the neural network. It takes over and controls the host’s behavior.”
“Why in the world would our ancestors bring along such a creature when they came from Earth?” asked Umbo.
“They didn’t,” said Olivenko.
“How do you know that?” asked Loaf. His tone showed he was still skeptical of Olivenko, who was only a member of the city guard in Aressa Sessamo, rather than a real soldier.
“Because if they had, it would exist in every wallfold,” said Olivenko, “and it doesn’t exist in ours.”
Olivenko thinks the way Father taught me, thought Rigg. Don’t assume: Think it through.
Vadesh was nodding. “A very tough little creature, the facemask.”
“What the humans of this wallfold named it. For reasons that would have become tragically obvious if you had bent over to drink from the stream.”
Something didn’t ring true about this. “How can a creature that evolved on Garden successfully take over the brains of creatures from Earth?” asked Rigg.
“I didn’t say it was successful,” said Vadesh. “And you are now as close as is safe. To avoid picking up facemasks from the wet ground beside the stream—they can attach to any skin and migrate up your body—you should follow in my footsteps exactly.”
They followed him in single file through the grass, with Rigg bringing up the rear. The path Vadesh took them on was the highest ground. Each time they reached a damp patch they jumped over it. The rill was narrow here. No one had trouble overleaping it.
Only when they got to higher ground several rods beyond the rill was Rigg able to continue the conversation. “If the parasite wasn’t successful, why is it still alive here?”
“The parasite is successful in attaching to humans and Earthborn beasts of all kinds,” said Vadesh. “But that’s not really how we measure success in a parasite. If the parasite kills its host too quickly, for instance, before the parasite can spread to new hosts, then it has failed. The goal of a parasite is like that of any other life form—to survive and reproduce.”
“So these facemasks kill too quickly?” asked Umbo, shuddering.
“Not at all,” said Vadesh. “I said ‘for instance.’” He smiled at Rigg, because they both knew he was echoing Rigg’s earlier testy reply when Vadesh told him his time estimate was off by a millennium.
“So in what way did this parasite fail?” asked Rigg—the way he would have pushed Father, an attitude that came easily to him, since not just in face and voice but in evasiveness, smugness, and assumption of authority this expendable was identical to the one that had taken Rigg as an infant from the royal house and raised him.
“I think that with native species,” said Vadesh, “the parasite rode them lightly. Cooperating with them. Perhaps even helping them survive.”
“But not with humans?”
“The only part of the earthborn brain it could control was the wild, competitive beast, bent on reproduction at any cost.”
“That sounds like soldiers on leave,” said Loaf.
“Or academics,” said Olivenko.
Vadesh said nothing.
“It sounds like chaos,” said Rigg. “You were there from the beginning, weren’t you, Vadesh? How long did it take people to learn of the danger?”
“It took some time for the facemasks to emerge from their chrysalises after the disaster of the human landing,” said Vadesh. “And still longer for the people of Vadeshfold to discover that facemasks could infest humans as well as cattle and sheep.”
“The herders never got infected?” asked Loaf.
“It took time for a strain of facemasks to develop that could thrive on the human body. So at first it was like a pesky fungal infection.”
“And then it wasn’t,” said Rigg. “Facemasks are that adaptable?”
“It’s not blind adaptation,” said Vadesh. “They’re a clever, fascinating little creature, not exactly intelligent, but not completely stupid, either.”
For the first time, it occurred to Rigg that Vadesh was not just fascinated by the facemasks, but enamored of them.
“They can only attach to their host in the water,” said Vadesh, answering a question no one had asked. “And once they attach to an air-breather, they lose the ability to breathe in water. They only get their oxygen from the blood. You know what oxygen is?”
“The breathable part of air,” said Umbo impatiently. Olivenko chuckled. Of course, thought Rigg—Olivenko was a scholar, and Umbo had studied for a time with Rigg’s father.
But Rigg noticed that Loaf and Param seemed to have no idea what Vadesh meant. How could air be divided in parts? Rigg remembered asking Father exactly that question. But there was no point in explaining the point now or soon or, probably, ever. Why would a soldier-turned-innkeeper and a royal heiress who had fled her throne require a knowledge of the elements, of the behavior of gases and fluids?
Then again, Rigg had thought, all through his years of education, tramping with Father through the woods, that he would never need anything Father taught him except how to trap, dress, and skin their prey. Only when Father’s death sent Rigg out in the world did he learn why Father had trained him in languages, economics, finance, law, and so many other subjects, all of which had proven vital to his survival.
So Rigg started to explain that invisible air was really made of tiny particles of several different types. Loaf looked skeptical and Param bored, and Rigg decided that their education wasn’t his job.
He fell silent and thought about parasites that could only attach to humans in water, and then they lost the ability to breathe on their own. Rigg filed the information away in his mind, the way Father had taught him to do with all s...