“I believe that when the expendable finishes explaining about the civilization on the binary planet, you’ll decide that ten of these twenty ships should jump to a spot much nearer the binary.”

“Will they still skip eleven millennia back in time?” asked Noxon.

“No. Curing the replications also cures the time skip.”

“Are you ready for me to explain about the binary planet?” asked the expendable.

“I am,” said Ram. “Unless the mice now command the ship.”

“They’ve fixed it so we don’t split into nineteen pieces every time we jump,” said Noxon.

“You asked them if we’re planning to jump again,” said Ram. “Why would we do that?”

“Let’s hear the expendable and find out,” said Noxon. “The mice apparently already know what he’s going to tell us.”

The expendable took a breath before proceeding. Such theatri­cality from a machine that doesn’t need to breathe, thought Noxon. “Earth’s Moon was important to the evolution of life, by causing tides and controlling other cycles,” said the expendable. “But this world is really two planets, nearly equal, as close as they can be without tearing each other apart with tidal forces.”

“So both have atmospheres,” said Ram.

“Both have life?” asked Noxon.

“Both have widespread electricity and radio communications,” said the expendable. “They each monitor the other’s radio broadcasts, and I believe the ability to interfere with and ­eventually control remote computer systems was developed by the nearer planet in order to use it against the farther one.”

“They have a million kilometers between them,” said Ram, “and they’re attacking each other?”

“That suggests reciprocality,” said the expendable. “The nearer planet is attacking the farther one. The farther one seems to be working only to protect their own systems against attack.”

“Let me guess,” said Ram. “The one that attacked us is this aggressive one.”

“I don’t know,” said the expendable. “Whichever world emerges victorious, it will be convinced that the only way to deal with aliens is to destroy them utterly.”

“So even if it’s the nice guys on the far planet,” said Noxon, “they might still be the enemy that attacks Earth.”

The alpha mouse spoke to Noxon. “We don’t know which one is our enemy. Both must be brought under control.”

“It seems wrong to punish one world for what the other world did,” said Noxon.

“We’re not punishing anyone,” said Ram. “We’re saving the human race against a threat, and we don’t know which of these worlds poses that threat.”

“We know that both of them pose a threat,” said the alpha.

“It’s possible that both pose a threat,” said Noxon. “But to take preemptive action against both seems unfair. Stifling a civilization, a species that might be completely innocent—”