“I wonder why.”

“A Pak wouldn’t see the point of taking a machine to think for him. He thinks too well already… and likes it too much, for that matter.”

The inside of the teardrop-shaped cargo pod was nothing like that of the alien ship that had come plowing into the solar system two centuries ago. Its cargo was death. It could sprout heavy attitude jets and fight itself. Its long axis was an X-ray laser. A thick tube parallel to the laser would generate a directed magnetic field. “It should foul up the fields in a monopole-based Bussard ramjet. Of course that might not hurt him enough unless your timing was right.” When Roy had learned how to use it — and that took time; he knew little about field theory — Brennan started drilling him on when.

That was the point at which Roy rebelled.

The past two months hadn’t been particularly pleasant. Roy was back in school, the only student of a full-time teacher who could not be snowed or evaded. He didn’t like being a child again. He missed the open spaces of Earth. He missed Alice. Hell, he missed women. And it was going to go on for five years!

Five years, and the rest of his life on Wunderland. He didn’t know that much about Wunderland, but he knew that its population was small and thinly spread, its technology just adequate. A pastoral paradise, perhaps; a nice place to spend one’s life… until Brennan arrived. Then Wunderland would go on a war footing.

“The Pak fleet is a hundred and seventy-three years away,” he pointed out now. “We’ll be at Wunderland in five years. What makes you think you need a gunner? What am I doing here, anyway?”

Brennan took a handhold at the rim of a fusion bomb’s rocket nozzle. “You could say I’ve learned some humility. I thought of looking for a Pak fleet, long ago, but I didn’t. The probability was just too low. Well, I’ve stopped taking chances.”

“What chances? We know where the Pak fleet is.”

“I didn’t want to worry you. It’s a long shot.”

“Worry me! I’m bored!”

“All right, let’s go back a bit,” said Brennan. “We know where the first fleet is, and how big it is. The second fleet wasn’t launched for another three-hundred-odd years. All I’ve found of it is a patchy source of those same chemical exhausts, off center to the first fleet and moving a bit faster. They wouldn’t follow directly behind the first fleet. It’d be eating up too much of their fuel.”

“How big?”

“Smaller. Order of a hundred and fifty ships, assuming they didn’t change the design, which they may have. I can’t tell.”

“Is there a third fleet?”

“If there is, I’ll never detect it. They had to go out for new resources to build the second fleet. They may have had to mine worlds in nearby systems and build the ships there. How long would it take them to build a third fleet? If it’s there, it’s too far away for me. But the point is that there had to be a last fleet.”

“So what?”

“I’m suggesting that when the last fleet left — the second or the third or the fourth, it doesn’t matter — some protectors stayed behind. We assume they were the ones without breeder descendants. They stayed behind partly to save room on the ships, and partly because they might do some good on Pak.”

“On an empty world? How?”

“They could build a scout fleet.”

It was not the first time Roy had worried about Brennan’s sanity. The changes in his physiology, plus twenty-two decades alone… but if Brennan were insane, he might be too bright to give it away.

Gently Roy pointed out, “But your scout fleet would be at least five hundred years behind the rest.”

“Sounds silly, does it? But they’re free to experiment. They don’t have to use a proven design, because they’re only risking themselves. They don’t need a cargo pod. They could take three gravities forever, I think; I know I could. That cuts down on their supply weight, because the trip takes less time. With the breeders gone they can do all kinds of things… like making new metal mines by setting up eruptions in the crust of Pak.”

“You’ve got quite an imagination.”

“Thank you. What I’m getting at is that they could plan to pass the first wave of refugee ships about where the Pak telescopes aren’t good enough to scout the territory any further. From there on they lead the fleet. Still bored?”

“No. You’re daydreaming, though. They might never have built these hypothetical ships. Whatever sent them scurrying out of the galactic core might have caught the scouts.”

“Hell, it could have caught the third wave and brushed the second. Or the scout ships might have blown up. Or — lest you miss the point of all this — they could be arriving now.”

“You haven’t found them?”

“What, with a whole sky to search? They wouldn’t just come down our throats; they’d converge on Sol from random directions. I would, if I were doing it. Remember what they’re expecting to find: a world of Pak protectors running a civilization two hundred years old. That’s enough time to build up a virgin world, starting with a population of… oh, thirty million breeders of all ages would have given Phssthpok about three million newly changed protectors. The scouts wouldn’t want to give away the position of their fleet.”

“Uh huh.”

“There is something I can do, but it’ll take a few days of work to make the tools. First I’m going to make sure you can fight this ship. Let’s go back to the lifesystem pod.”

A directed magnetic field would churn the interstellar plasma as it was guided into a Bussard ramjet. As a weapon it might be made to guide the plasma flow across the ship itself. The gunner would have to vary his shots, or an enemy pilot could compensate for the weapon’s effect. If the local hydrogen density were uneven, that would hurt him. If the plasma were dense enough locally, the enemy could not even turn off his drive without being cremated. Part of the purpose of the ram fields was to shield the ship from the gamma ray particles it was burning for fuel.

“Hit him near a star, if you get the choice,” said Brennan. “And don’t let him do that to you.”

The laser was surer death, if it hit a ship. But an enemy ship would be at least light-seconds away at the start of a battle. It would make a small, elusive target, its image delayed seconds or minutes. The thousand mile wings of a ram field would be easier to hit.

The guided bombs were many and varied. Some were simple fusion bombs. Others would throw bursts of hot plasma through a ram field, or carbon vapor to produce sudden surges in the burn rate, or half a ton of pressurized radon gas in a stasis field. Simple death or complicated. Some were mere decoys, silvered balloons.

Roy learned.

The wreck of Kobold was almost three months behind them, and Roy was at war. Lately he had come to enjoy these simulated battles, but he wasn’t enjoying this one. Brennan was throwing everything at him. The Pak scouts had used a three gee drive until they crossed his wake, and then Wham! Six gees and closing. Some of his missiles were going wild; the scouts were doing something to the guidance. The pair dodged his laser with such ease that he’d turned the damn thing off. They’d used lasers on him, firing not only at his ship but at the field constriction behind him where hydrogen atoms met and fused, so that Protector surged unevenly and he had to worry for the generator mountings. They threw bombs at unreasonable velocities, probably through a linear accelerator. He had to dodge in slow random curves. Protector was not what you’d call maneuverable.

Three days he’d been in the lifesystem module, eating and drinking there and using pep pills instead of sleep. Playing Brennan’s game. He was mad clean through. Within ships he could infer only from instruments, he imagined hard faces like Brennan’s.