“The energy cost of maintaining that strong a field can only be paid once, using the heat gathered during reentry. In the ocean, it would have to last thousands of years under relentless pressure. And it still might be found.”

“It might be found because of the fields,” said the expendable. “Don’t forget that it’s technology from Earth that creates those fields. There is no chance that such a field anywhere on or under the planet’s surface will go undetected once we get close to the time when the ship was built.”

Again, the mice were full of suggestions. Noxon sorted them out and relayed the most cogent one. “The mice keep saying to put it under the ice.”

“We can go back in time before the top hundred meters of Antarctic ice formed,” agreed the expendable. “But either the ice will crush the ship, or the fields that prevent the ice from doing so will give away our location years before this starship was built.”

Noxon and Ram Odin looked at each other in glum silence.

Inside Noxon’s clothing, the mice gathered and murmured to each other and then settled into a chant: “Stupid stupid stupid.”

“The mice are saying that we’re stupid,” said Noxon. To the mice he said, “Do you include yourselves in that? Or do you have some obvious solution that we’ve overlooked?”

The explanation, when Noxon understood it, was charmingly simple. “Oh, of course,” he said, and then relayed it to Ram Odin. “The mice suggest that the ship doesn’t have to survive intact. Park it a hundred thousand years back, at the beginning of the last glacial period, and then let the ice crush it and grind it. We aren’t going to use it at the end of that period, we just need it not to be found, and not to give off detectable signals or heat or fields of any kind.”

Ram Odin nodded. “We’re going to go back in time and pick it up right after we left it there. When it’s still virtually brand-new. So what happens to the ship a week after we park it there is irrelevant.”

“Not completely,” said Noxon. “For instance, if we left the mice on the ship and they took it over, they could lift it off the surface long before the ice formed any kind of impediment. Then they could destroy the human race before it became numerous, and have the planet to themselves.”

The howls of protest from the mice were loud enough that Ram Odin could hear them, though he couldn’t distinguish any of their words.

“They’re saying,” said Noxon, “that they would never do that and it didn’t even cross their minds and shame on you for thinking them capable of such treachery.”

“You believe them?” said Ram Odin.