“The Others moved farther and farther out, for their own protection. Meanwhile, their individual life spans increased, up to what seemed to be a natural limit. They couldn’t push it far beyond about eight hundred years, with half of that life span in reduced circumstances . . . basically, alive and alert, but maintained by machines. You see where this would lead?”

It was asking the question of me. “They would . . . devalue what we would call ‘normal’ life? In favor of life partnered with machines? There’s something like that going on on Earth, even now.”

“Really? The Others might want to get in touch with them.”

“That would be fun,” Elza said. “Some of them are halfway aliens already.”

Spy looked at her with an unreadable expression. “Most of this I knew from Other-prime. But Fly-in-Amber added a turning point, a missing link.

“The final separation between the two groups came about when the Others discovered free power, the ability to bleed energy from an adjacent universe.”

“The same as our source of power,” Fly-in-Amber said.

“That’s right. You got it from them, though I take it that neither Martians nor humans really understand how it works.”

“Only how to use it,” Paul said.

Spy nodded. “This discovery allowed the Others to put a safe distance between themselves and the enemy, to move out to Wolf 25’s dark companion.

“They thought that this would make their physical separation complete. At almost the same time, they took total control of their life processes and abandoned their carbon-based form in favor of the virtually immortal bodies they have now.”

“So they downloaded their minds,” Paul said, “into artificial creatures with low-temperature body chemistry.” The Others had told us that their version of organic chemistry was cryogenic, based on silicon and liquid nitrogen.

“It wasn’t as simple as transferring information. Each individual had to die, and hope to be literally reborn in its new body.”

“They had no choice?” I said.

“Apparently they did. But the ones who didn’t change died out long ago.”

“Probably helped along by their successors,” Namir said.

“That could be. I don’t know.

“What I do know is that the ones left behind on this planet grew fearful. So they began building this huge invasion fleet.”

“Why on the ground, I wonder,” Paul said. “If they’d put them together in orbit, the ships wouldn’t have to be streamlined. And the net energy saving would be huge.”

Namir laughed. “They wouldn’t have to worry about that. They couldn’t have done this if they didn’t also have the free-energy thing.”

“And that was really what doomed them,” Spy said. “Even without the huge fleet, their discovery of the power source put them essentially next door to the Others.”

Unlike us, I hoped to think.