“We can,” said Noxon. “We can always decide not to establish colonies on either world.”

“That’s not an option,” said Ram. “We’re here to neutralize the threat. We have no way of monitoring whether we’ve succeeded without establishing a permanent, technologically powerful presence.”

“That’s not really true,” said Noxon. “For instance, we could drop off the mice a million years ago and then pop back to this time to see where we stand.”

Ram laughed. “We’d find that the mice were completely prepared to destroy us, take over our ship, fly back to Earth, and take over everything.”

“We would never,” said the alpha mouse.

“I was just pointing out that if we establish human colonies, it’s because we want to, not because there’s no other way,” said Noxon.

“Well,” said Ram, “whatever we do, I don’t propose to leave it all up to the mice.”

“The other ships have all decided to go back and test the proteins on both worlds,” said the expendable.

“How do we divide the fleet?” asked Ram.

“The computers have already divided the ships randomly into two groups of ten. We’re in the group that stays at this near world, while the others jump the fold to the far one.”

“The one with the tripods,” said Wheaton. “That’s a shame—I was most interested in studying them.”

“That’s how all the Wheatons felt,” said the expendable. “But then they all decided that both species need to be studied, so half the Wheatons have to take the second choice.”

Wheaton sighed. “I suppose for every Professor Wheaton who lost, there’s a Professor Wheaton that won.”

“Depending on how you define ‘won’ and ‘lost,’” said the expendable. “You could say that they all win, with an entirely new sentient species to study.”

“I feel much happier already,” said Wheaton.

“Ironic or sincere?” asked the expendable.

“Pissed off but compliant,” answered Wheaton.

Noxon sliced them through the time it took for the ship to fly into stationary orbit around the near planet. At Noxon’s insistence, the mice stayed on the ship with him and Ram, as Wheaton and the expendable flew down to the surface. “The scientist and the robot can do the job perfectly,” said Noxon. “The time traveler and the pilot have to stay here, in case we have to undo something horrible the mice have done.”

“So untrusting,” said the alpha mouse.

Noxon regarded this comment as not worth answering.

Wheaton and the expendable made frequent reports during their days of data collection. Ancestors of the scuttling aliens were easy enough to spot—they were already as close to sentience as, say, Homo habilis. Using tools, but not yet making fire. “It is difficult for Professor Wheaton to stay focused on the project at hand,” said the voice of the ship. “He keeps wanting to go backward and forward and the expendable has to keep reminding him that only Noxon can do that.”