“So they can take preventive measures and cause us all not to exist?” asked Ram Odin.

“They wouldn’t cause us not to exist,” said Rigg-the-killer. “Preservation of causality and all that. But yes, it might cause them to prevent the terraforming of Garden in the first place. What about that?” he asked Rigg Noxon. “Do we leave the ­jewels behind? If we do, the ship will process us as stowaways and have the expendables put us into stasis or just kill us.”

Rigg Noxon shook his head. “No. Remember what Umbo learned in his reading in the library in Odinfold? The Odinfolders—or the mice, who can tell?—worked out the math of what happened in the jump. It didn’t just create nineteen copies of the ship and all the humans and machinery on it. It also made either one or nineteen other copies that moved exactly backward in time.”

“So what?” asked Rigg-the-killer. “They’re moving backward in time. Even when we jump around, at the end of a jump we’re still moving forward in time, the same direction as the rest of the universe. And the backward movement of the ship or ships would exactly duplicate the forward voyage of the ship coming here, so we’d still be inside the ship that voyaged out. We’ll never be able to find the backward-moving ship. Or ships.”

“Not with the skill set we’ve had up to now,” said Rigg Noxon. “But what if we could learn to go the other direction?”

“What if we could jump straight to Earth without using any starship at all?” asked Rigg-the-killer. “Because we can’t. There’s no reason to think we can.”

“I think Param holds the key,” said Rigg Noxon.

“She slices time very thin, but she still moves forward in time.”

“Because all she knew was slicing,” said Rigg Noxon. “She couldn’t jump forward or backward, the way we can. Now, with our facemasks, we can slice time the way she does. We can see those tiny divisions and do something about them. But we can also jump backward. We can slice time backward.”

“We’re still moving forward,” said Rigg-the-killer. “Between slices.”

“So what?” asked Noxon. “If we slice time thin enough, and we jump backward two nanoseconds, stay there for one nanosecond, and then jump backward another two nanoseconds, the effect is that we move backward in time at the rate of one nanosecond per nanosecond, which is the same rate that the back-traveling ship will be moving backward through time.”

“But when we’re in existence, we’re going forward,” Rigg-the-killer insisted. “No matter how fine you chop the time.”

“Maybe you’re right,” said Noxon. “But you’re forgetting the very first thing we ever did. We saw a path, Umbo slowed it down for us, and we latched on. That was how we jumped, by latching on to a person. If we can at least detect a backward-­moving person’s path, we can attach and it will change our direction.”

“Or maybe not,” said Rigg. “Maybe forward-time and backward-­time annihilate each other when they touch, like matter and anti-matter.”

“So I’ll do it alone,” said Noxon. “I’m the extra copy, right? So if I get annihilated, we’re back to the right number of Riggs, that’s all.”

“And then,” said Ram, “you can take hold of the backward-moving version of me and pull me—him—back into the normal timestream again.”

“Just what we need,” said Rigg. “More Ram Odins.”

“I’ve shepherded nineteen wallfolds for eleven thousand years,” said Ram. “What have you done?”

“You hurt his feelings,” said Noxon.

“He’s too sensitive,” said Rigg.

“You do realize that there was a time-jump of 11,191 years. Not to mention a leap of several lightyears through folded space. Do you think you can hang on through that much time and space and a change in direction?”

“It’ll be interesting to see,” said Rigg. “We’ll find out by trying it.”

“We’ll find out,” said Noxon, “but I’ll do the trying.”

“You get all the fun with physics?” asked Rigg.

“I’m the extra. We can afford to lose me.”

“Well, I can,” said Rigg. “But you can’t.”

“I won’t be around to miss me when I’m gone,” said Noxon.

“I’m not sure how your brains even function,” said Ram. “Everything you say makes no sense. And it’s perfectly sensible.”

“We can both go back, but on different ships,” said Noxon to Rigg, ignoring Ram. “I’ll latch on to the backward ship and ride it to Earth, and you hide on the original ship and jump back to the beginning of the voyage.”

“You both get there at exactly the same time,” said Ram. “The beginning of my voyage.”

“Not really,” said Rigg. “When I get there, if I do it, I have to deal with the fact that I’m in the same timeflow. If I don’t slice time or jump, I’m visible. But Noxon, he arrives there completely invisible. And in an invisible ship. I’ll be there without any friends, because I can never show myself during the voyage.”

“Why not?” asked Ram.

“Because I didn’t,” said Rigg. “It was you on that voyage. Did you see me? If you had seen me, there’s a good chance it would have derailed the entire sequence of events. Leading to the nonexistence of nineteen colonies on Garden.” He turned to Noxon. “You see the danger? One slip, and you might undo everything.”

“But I won’t have to hide from the Ram on my backward ­voyage, because he’s a post-voyage Ram,” said Noxon. “He’s not causally connected to this universe, so I won’t change anything at all. And I’ll have a ship that isn’t buried under a million tons of rock.”

“Moving backward in time,” said Ram.

“If I can pull myself and the backward Ram Odin into the forward-flowing timestream, I should be able to pull the ship with us. Material objects can be dragged along.”

“If your venture succeeds,” said Rigg, “then I won’t need to go back with the Visitors. For all I know, the Visitors will never come at all.”

“So while I go to Earth, you’ll stay here?”

“If you succeed, then the world of Garden won’t be destroyed,” said Rigg. “So while you’re playing God back on Earth—”

“You’ll play God here,” said Noxon.

“Visit all the wallfolds,” said Rigg, “and decide whether to bring the Walls down.”

“Or some of them, anyway. Keep the dangerous ones quarantined,” said Noxon.

“Keep the technologies of Odinfold and the facemasks of Vadeshfold and the power of the expendables out of the hands of Mother and General Citizen,” said Rigg.

“So you’re going to make a play to be King-in-the-Tent?” asked Noxon. “They’ll be eager to follow you, with your pretty face.”

“I’ll set up Param as Queen-in-the-Tent. Or abolish the monarchy and the People’s Revolutionary Council,” said Rigg. “I have no plan.”

“Yet,” said Ram Odin.

“I’ll have a plan when I need one,” said Rigg.

“In a pinch, plans kind of make themselves, mostly because you don’t have a lot of choices,” said Noxon.

“Aren’t you going to ask the advice of someone older and wiser?” asked Ram Odin.

“When we find somebody wiser,” said Noxon, “we’ll ask him for advice.”

CHAPTER 2

Council in Larfold

“What are we waiting for?” asked Param.

“We’re not waiting at all,” said Olivenko. “Go. Do whatever it is you’re so eager to do.”

“There’s nothing to do,” said Param.

“Then we’re not waiting,” said Olivenko. “We’re merely purpose­less. Find a purpose, and go accomplish it. You don’t have to wait for anything.”

“What purpose is there? We know the world ends in a very few years. What’s the point of starting anything?”

“I’m sure Umbo will take you back in time, as far as you want,” said Olivenko. “You can marry and have babies. Raise an army and conquer a wallfold. Assassinate General Citizen before he meets your mother. So many exciting possibilities.”