Two scouts closing from behind, and finally he hit one with the directed magnetic field and watched its ram field flare and dissipate.

That was when he realized that there were two pairs of ships in tandem. Damn Brennan anyway! He’d hit a lead ship, but the trailing ship was still there… and slowing. Somehow the loss of the lead ship had slowed it. Roy concentrated on the second team, which was still closing.

He tried a turn. Two ships linked should be less maneuverable than one… and an hour later he knew that they were. He’d turned only a fraction of a minute of arc, but they had turned less. He could keep up his dodging and still turn inside them.

He tried some of his weaponry on the lone ship behind him.

Then half his weapons board was red, and he had to guess what had exploded in the trailing pod. Probably that idiot projector: he’d been trying to punch a hole in the lone ship’s ram field. He bet his ship he was right, and gambled further that the explosion had wrecked his laser, which might otherwise have been of some use. He fired a flurry of bombs from the side of the cargo pod opposite the explosion. The lead ship of the remaining pair flared and died.

That left two, each the trailing ship of a pair, making less than his own acceleration. He dithered a bit, then ran for it. He continued to dodge missiles and laser beams.

The scouts fell away. He watched them dwindling… and then one wasn’t dwindling… and it finally dawned on him that that one had picked up acceleration somehow and was coming up from behind at something like eight gees.

Roy’s first impulse was to scream, “Brennan! What are you trying to pull?”

He’d done that before. This time he restrained it. Because he’d guessed the answer: the second ship was burning Protector’s own exhaust! Never mind how: that was it, that was why they moved in tandem.

He dropped two half-tons of radon with the drives disconnected.

Radon has a short half-life: it has to be kept in stasis. The generator was outside the bomb shell, and was partly soft iron. The enemy’s ram field tore it apart. A minute later the radon was in the constriction, and incredible things were happening: radon fusing to transuranian elements, then fissioning immediately. The constriction exploded. The ram field sparkled like a department store Xmas tree gone manic. The Pak ship flared into a small white point, fading.

The last Pak ship was far behind.

Coming out of it was a slow process. Roy had to keep telling himself: this isn’t real, this is only pretend. He jumped violently when Brennan’s alien head poked through the twing.

Then he shouted, “What the hell was that about, him burning my exhaust?”

“I just knew you’d bring that up,” said Brennan. “I’ll tell you in detail, but first let’s talk about the battle.”

“Screw the battle!”

“You did well,” said Brennan. “There isn’t much left of your weapons pod, but that’s okay if you don’t meet any more scouts. You don’t have reserve fuel to get into orbit around Wunderland; you used too much. But you can abandon Protector and land with the cargo ship.”

“That’s nice. That’s very reassuring. Now tell me how a Pak scout can burn my own exhaust and come tearing up my tailpipe!”

“It’s one possible configuration. In fact, it’s the one I’m about to start looking for, because it’d be easy to find. I can show you better with diagrams.”

Roy had calmed down a bit when they reached the Flying Dutchman’s control room. He had also started to shake. Three days in Protector’s control chair had left him exhausted.

Brennan looked at him thoughtfully. “Want to put this off?”

“No.”

“Okay, I’ll make it quick. Let’s look at what your ram field does. It picks up interstellar hydrogen in a path three thousand miles across. It sweeps it in via magnetic fields, pinches it together hard enough and long enough to produce some fusion. What comes out is helium and some leftover hydrogen and some higher-order fusion products.”

“Right.”

“It’s also a hot, fairly tight stream. Eventually it’ll spread out into nothing, like any rocket exhaust. But suppose a ship were following you, here.” Brennan made pictures on the screen: two tiny ships, the second following a hundred miles behind the first. He spread a wide cone before the lead ship, converging it almost to a point behind the ship. A needle shape with the ship in its point — the ship’s protective shield — brought the incoming hydrogen into a ring shaped constriction.

“You’re collecting the fuel for him. His ram field is only a hundred miles across—” Brennan drew a much narrower cone. ” — and it gives him finer control over his fuel flow. It’s already hot and dense. It burns better, in higher-order fusion. The exhaust would be rich in beryllium.

“It’s just one of the things those last remaining Pak might have tried. The lead ship would be nothing but a ram: no onboard fuel, no insystem motor, no cargo. It would have to be towed up to ramscoop speed. The following ship is heavier, but it gets more thrust.”

“You think that’s what’s coming at us?”

“Maybe. There are other ways to work it. Two ships, independent, held together by a gravity generator. In a pinch they could split up. Or the lead ship might be the ship proper, with the hind ship only an afterburner. Either way, I can find them. They’ll produce beryllium frequencies like a neon sign on the sky. All I’ve got to do is build the detector.”

“Need help?”

“Eventually. Go to sleep. We’ll try another dry run in a month or so.”

Roy stopped in the doorway. “That long?”

“Just to keep you on your toes. You’re as ready as you’ll ever be. Only, be more careful with that electromagnetic projector. When you wake up I’ll show you what the Pak scouts did to it.”

“What you did to it.”

“What they would have done. Go to sleep.”

Brennan was in the machine shop for three days. If he slept he slept there. He skipped meals there. Whatever he was doing filled the machine shop with constant racket and sent a humming vibration through the rock of the Flying Dutchman.

Roy read a couple of old novels stored in the computer. He floated through bare rock caverns and corridors, and was oppressed by the sensation of being underground. He worked himself to exhaustion in the exercise room. Free fall had cost him some muscle tone. Have to do something about that.

He researched Wunderland and found about what he expected. Gee: 61%. Population: 1,024,000. Colonized area: 3,000,000 square miles. Largest town: München, population: 800. Farewell, city life. Come to that, München would probably look like New York to him by the time he got there.

There was a time on the fourth day when he found the machine shop quiet and Brennan apparently asleep. He was about to leave when Brennan opened his eyes and started talking.

“You depend too much on those long, slow turns,” he said. “The way to dodge Pak weaponry is to vary your thrust. Keep opening and closing the constriction in the ram field. When they throw something like a laser pulse into the constriction, open it. Nothing’s going to fuse if you don’t squeeze the plasma tight enough.”

Roy wasn’t flustered. He was getting used to Brennan’s habit of resuming a subject that may have been broken off days ago. He said, “That last ship could have done that when I threw radon at him.”

“Sure, if he did it fast enough. At good ramscoop velocities the shit should be in the constriction before he knows it’s reached the ram field, especially as you didn’t put any rocket thrust on it. That was good thinking, Roy. Memo for you: don’t ever follow a ship that’s running. There are too many things he can throw into your ram field. Hopefully we’ll be doing the running in any battle.”