“For now,” said Param. “Till we go back.”

“And why would we go back?” asked Loaf.

“To get the last jewel,” said Param. “To shut off this last Wall.”

“So you think we should do what these expendables intend for us to do?” asked Rigg.

“I think they’ll give us no peace until we do,” said Param. “I think his supposed obedience is a fraud, and they’re going to keep controlling us the way they’ve been doing all along.”

“In case anyone’s forgotten,” said Olivenko, “not all the people in other wallfolds are nice. Not even the people in our wallfold are nice. What would General Citizen do, if this Wall disappeared right now?”

“Come over here and kill us all,” said Umbo.

“Not if I killed him first,” said Loaf.

“Wars of conquest,” said Olivenko. “Until now, the great achievement of the Sessamoto was to unite the entire wallfold under a single government. But if the walls disappear, how long before we try to conquer the world? Or the people of some other wallfold try to conquer us? Humans are humans, I assume, in every wallfold.” He turned to the expendable. “Or has human nature changed in any of them? Is there a version of the human race that has abandoned predation and territoriality?”

“I wouldn’t know,” said the expendable. “We pretty much stick to learning about our own wallfold.”

Rigg said, “Then ask the others. Find out. If you want us to take down the Walls, we have to know the consequences.”

“I think that’s something that you’ll need to discover for yourselves,” said the expendable.

“So much for obedience,” said Param.

The expendable turned to her. “The Walls have never been shut off before, or crossed, until the five of you. We don’t know how the human beings of each wallfold will react. I cannot tell you what I do not know. I told you that I would obey any command that I had the power to obey.”

“So the responsibility for the whole world is in our hands,” said Rigg.

“Your hands,” said Umbo. “You have the jewels.”

“Come on,” said Rigg. “We’re in this together. Please.”

Umbo laughed. “Lighten up, Rigg. What else have we got to pass the time, if not taking down all the Walls in the world?”

“And finding out what they’re not telling us,” said Param. “Count on it, they’re still lying to us. You notice he’s not even denying it.”

The expendable regarded her calmly. “I’m not agreeing, either.”

“Which is just another form of lying,” said Param.

“You cannot lie,” said the expendable, “if you do not know the truth. You can only be wrong, or silent. I prefer silence to error, and since I do not know when I am in error, silence is the best choice unless I am forced to speak.”

“Not just a liar,” said Param, “but a philosopher.”

“Tell us the truth when we ask you questions,” said Rigg, “or whatever you believe to be the truth based on current information. And answer everybody’s questions, not just mine.”

“All right,” said the expendable.

“What is your name?” Rigg asked the expendable.

“I don’t have a name,” said the expendable.

“But I need a name for you. And a name for the one I called Father.”

“The active expendable is referred to by the name of the wallfold in which he serves,” said the expendable.

“So what is the name of that wallfold? The one we were born in? The one we just left?”

“We call it Ramfold,” said the expendable. “So we call your active expendable ‘Ram.’”

“And this wallfold?” asked Umbo. “And your name?”

“Vadesh,” said the expendable. “This is Vadeshfold, and I am called Vadesh.”

“Did you notice that he actually answered somebody who wasn’t me?” said Rigg. “That’s progress.”

“Is there fresh water around here?” asked Loaf. “Drinkable water? Clean water? Safe water? In quantities we can use to refill our water bags—do I need to be more specific?”

“I’ll lead you to water,” said Vadesh. “But I can’t make you drink.”

Rigg looked at the others, puzzled, then turned back to Vadesh. “Why would you say that? Why would you need to make us drink?”

“It’s an old saying,” said Vadesh. “On Earth, the world where the human race was born. In one of the languages of Earth. It is twelve thousand years old. ‘You can lead a horse to water, but you can’t make it drink.’”

“Thank you for the history lesson,” said Olivenko.

“And the lesson in equine behavior,” said Param.

Rigg chuckled at their ironic humor as Vadesh led them away from the Wall, toward a not-so-distant line of trees. But he noticed that Vadesh made no comment on their jests, and a thought occurred to him. “Vadesh,” he said, “your references to the world where humans came from, and teaching us a saying from twelve thousand years ago. Is there some reason why we might need to know about Earth?”

“Yes,” said Vadesh.

“And what is that reason?” asked Rigg.

Vadesh said nothing.

“Does your silence mean that you don’t know?” asked Rigg. “Or that you just don’t want to tell us?”

“I cannot predict the answer to your question with anything approaching accuracy or certainty. But you will need to know many things about Earth, and you will need to know them soon.”

“Why?” asked Rigg.

“Why what?”

“Why will we need to know many things about Earth, and why will we need to know them soon?”

“Because they are coming,” said Vadesh.

“Who is coming?” asked Param.

“People from Earth.”

“When?” demanded Loaf.

“I don’t know,” said Vadesh.

“What will they do when they get here?” asked Umbo.

“I don’t know,” said Vadesh.

“Well, what can they do?” asked Rigg.

Vadesh paused. “There are billions of correct answers to that question,” said Vadesh. “In the interests of time, I will prioritize them.”

“Good,” said Rigg. “What is the most important thing they can do?”

“They can blast this world into oblivion, killing every living thing upon it.”

“Why would they want to do that?” asked Olivenko. “What have we ever done to them?”

“I was asked what they can do, not what they will do. And before you ask, I do not know what they will do. There are billions of answers to the first question, but there is no answer at all to the second. That is the future, and it’s a place where even the five of you can’t go, except slowly, a day at a time, like everyone else.”

“Here’s the water,” said Rigg. “It looks good. Let’s fill up the water bags, and drink.”

ACKNOWLEDGMENTS

Neil F. Comins didn’t know he was helping me with this novel when he wrote What If the Earth Had Two Moons?: And Nine Other Thought-Provoking Speculations on the Solar System, but I thank him anyway. His book is the reason why the planet Garden has a ring instead of a moon, and why I had the nineteen ships strike the planet the way they do. He is not responsible, however, for the things I made up that are not possible within the limits of known science.

The games with time travel that I play in this book are in deliberate defiance of the consensus rules of science fictional time travel. I decided that I was not going to avoid paradox, I was going to embrace it, adopting a rule set in which it is causality that controls reality, regardless of where it occurs on the timeline. After all, if we can postulate folding space in order to jump from one location to another instantaneously, why not fold time? And if we can retrace a path through space, why not retrace it through time?

One of the difficulties in explaining the events in this novel is that no point-of-view character ever has the full picture, which means I had no choice but to hope that readers would make the connections themselves. For those who are still confused, here’s a brief explanation of what “really” happened: When Ram’s ship entered the fold in space, the nineteen computers on board generated nineteen separate calculations, which created nineteen separate sets of fields. These interacted with Ram’s own mind, and Ram’s own strange ability with time caused each of those fields to be separately effective. That is, the jump was made nineteen times, creating nineteen copies of the ship going forward and nineteen copies going backward.