“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.”