Maybury made a small choking sound behind him. "They're coming," she announced.

Jameson looked out the other port. s.p.a.ce was filled with a sudden hail of fire. Over a front that must have been a hundred miles across, streaks of light lengthened and shrank to points again, like golden straws tumbling among the stars.

"That was their turnover point," Jameson said. "They're halfway across. Decelerating at one g, they'll be here in minutes."

Li looked up from the console, his blunt peasant face smeared with grime where he'd wiped away sweat with stained fingers. "All through now," he said. "Safety override is off. Now we should put it through test sequence."

"No time," Jameson responded. "We'll have to take our chances." He spoke into the mike pickup.

"Gifford, hear this. Tell the men they have thirty seconds to find something to grab on to. We're moving."

He switched off before Gifford could object. Some of the men must have been listening through their own circuits. There was a scramble as stuffed blue dolls wrapped themselves around stanchions, hooked themselves onto safety rails. Immediately under the port, Jameson saw Smitty wriggle out from beneath the lander and glide belly-down along the hull until she found a grip.

He settled down in the pilot's seat beside Li, and the two of them began to run through the newly edited checklist for powering the vehicle. Maybury crouched behind them, lightpad in hand, helping them keep track of all the changes.

It felt strange to be doing it this way, after all the months of training. He and Li had honed themselves for one purpose: to land the spidery craft on the surface of Jupiter's second-largest moon. The lockers behind them were crammed with geological equipment. The little boxy hovercraft for exploring Callisto's surface was still folded in its bay. Now the lander would never touch down. It had been turned into a tugboat.

The main engine fired, and the cabin shook with unplanned stresses. A few seconds later, Jameson saw through the port that Gifford had ignited the strapped probes by radio signal. Little jets flared along the shaft of the main ship and along the circ.u.mference of the ring, as Kay and Yeh compensated for the irregularities in direction of the thrust.

There was no sensation of movement yet. The buildup was going to be slow, slow.

Maybury's voice came hesitantly. "Maggie's calculations were correct, you know. This won't break us out of orbit."

Without turning his head, Jameson said, "You checked her figures, then?"

"Yes," Maybury answered in a small voice.

"It doesn't matter," said Jameson. "We'll get ourselves into a return trajectory later. All I want to do now is get us moving!"

Slowly, like a freight train being pushed along the tracks by an elephant, the great wheel-and-axle of the Jupiter ship responded. Jameson could feel the first faint suggestion of weight on the seat of his pants.

There was visible movement against the grid of stars, some of it lateral as the ungainly ma.s.s shuddered to align itself.

It wasn't good enough.

Outside the port, s.p.a.ce was alive with beams of light, flashing on and off as thousands of Cygnans made their final correction maneuvers. They were close enough to be visible through the port, little squirming golden worms clinging to matchsticks.

"Tod,p'eng yu ," Li said, staring straight ahead. He'd used the word for "friend," not "comrade." "I want you to know. I'm sorry. None of it was my idea."

Outside, trapped on the hull, one of the Chinese missile men lost his nerve and threw a wrench at the naked creatures swarming on their broomsticks. It tumbled harmlessly past one of the nearer Cygnans, who oozed sidewise to avoid it.

"What will they do?" Maybury wondered aloud.

Jameson shifted in his seat. "We've got nukes aboard," he said. "We ran through their ship like weasels in a chicken house, killing. What would you do?"

Maybury's hand, small as a child's, was clutching his, the nails digging into his palm. Li stared out the window, saying nothing. Outside, Gifford's work party had drawn together in a small defensive group, their movements hampered by the necessity of using a hand to keep from drifting away under the ship's gentle acceleration. The Cygnans had no such problem. Some of them already had touched down, anch.o.r.ed to anything handy by whatever hand or foot was convenient, like sea polyps swaying in a current. At the head of the ship they were crawling like maggots all over the observation bubble.

"Oh!" Maybury gasped.

Jameson jerked his head around to see what had startled her. She was staring, wide-eyed, toward the Cygnan fleet in the distance. At this angle it could be seen against the dark. They'd moved far enough by now so that it hung like a cl.u.s.ter of shiny grapnel hooks above the raw and b.l.o.o.d.y carca.s.s of Jupiter.

The laser light was flashing between them again. The figure of the five-pointed star within the pentagram did not appear again. Instead there was a shifting play of spiky forms as each ship in turn sent out brief tendrils of light to all its companions. A succession of clawed figures, looking like Greek or Hebrew letters, flamed red against the face of night.

Jameson could not guess at the message content. But the flashing signals galvanized the Cygnan horde.

Like shiny midges, they rose by the hundreds off the crippled ship and wheeled and darted in a forming swarm. A thousand beacons lit the night, and then they were vanishing, a cloud of distant sparks heading with incredible velocity toward the ships beyond.

"They're gone!" Maybury said wonderingly.

Jameson looked across at the barbed shapes of the ships hovering over Jupiter's ripe and swollen orb, still semaphoring their sins and psis and lambdas, drawing fiery scratches in the void.

"Not quite yet," he said.

They were four million miles out, well past the orbit of Callisto, when it happened. The feeble engines of the probes and missiles had not yet set them free, but had put them in a loose elliptical orbit that would carry them outside the orbit of Jupiter VII. Mike, Quentin, and the three Chinese fusion techs were working round the clock. Everybody pitched in to help: Maggie and Maybury on the engine-room computers, Jameson and Li and Fiaccone unplugging the damaged outside structures. Jameson had pa.s.sed Maggie a couple of times in the corridors without speaking to her.

Now Jameson slumped, exhausted, in a contour seat on the ship's bridge. Mike had promised boron fission within a couple of hours. The last missile rocket engine had been expended.

"What if they come back?" Kay asked, looking at him with red-rimmed eyes through a strand of straggling hair. "Even when we get going, we can only accelerate at a hundredth of a g. They can catch up to us in a few hours, any time they feel like it."

Jameson looked out through the big bubble at Jupiter's bright sphere. Io, or the sodium glow that surrounded it, was visible as a fuzzy yellow golfball that from this angle seemed to be poised just above Jupiter's eastern edge. The Cygnan ships were invisible, but they could be seen through a telescope as a glowing pentad hovering close to Io, keeping its bulk between them and the giant planet. They had transferred their orbit from their own moon, the one they had brought with them, to Io with its closer position, a bit over a quarter of a million miles from Jupiter. The pentacle of laser light was evidently a calibrating device as the five ships fine-tuned their new joint orbit.

"That's not what I'm worried about," Jameson said. "They're ready to move, all right. Those ships started changing their orbit about three seconds after the boarding party got back to them. What worries me is being this close to Jupiter. If we're still in orbit around it when they start moving, we'll go right along with them. And we don't have Io to shield us from radiation once they start moving through interstellar hydrogen at close to light speed."

"We be dead long before that time," Yeh grunted from his console. His lumpy face was lined with fatigue. He had worked without rest since reaching the ship.

Jameson nodded. "If we didn't get torn loose by the sun and fry to death, it would be hunger, decompression, or systems failure. Take your pick. We'll be lucky to nurse this wreck back to Earth in one piece."

"Bye dzwe na-yang!" Yeh suddenly bellowed. "Don't touch that!"

The feathery humanoid s.n.a.t.c.hed its hand away from the control board, its teddy-bear face looking somehow hurt. It rewarded Yeh with a bad smell, something like rotten eggs, and pranced off to join its friend over at one of the scattered monitor screens on the floor.

"Mischievous little devils, aren't they," said Kay.

Jameson watched the rosy-furred creatures fiddle with the console. They had somehow managed to conjure up a star chart. Now one of them was making peeping field-mouse noises, rolling the display, while the other one danced around in front of the view window, pointing at constellations.

"These two aren't the simple hunters they seemed to be, any more than we still are," Jameson said. "They come from a technologically advanced civilization. They were trying to show Mike something about how the Cygnan broomstick worked until he threw them out of the engine room. I think that before we get back home they'll be helping us man this ship."

The pink bipeds had been an invaluable help with the Cygnan prisoner, keeping it tranquilized and getting it settled in a cage-a cage, Jameson reflected, that was probably less comfortable than the one he'd been confined in aboard the Cygnan vessel. The Cygnan was in Kiernan's care now. It would have a lot of hamsters for company if Kiernan could get a few of the frozen ova in his files to start dividing. The humanoids had painstakingly sniffed every food and biological sample that Kiernan had shown them to try to improvise a diet that would keep the Cygnan alive until they got back to Earth. One of the things it could eat, surprisingly, was turkey, so it was going to get everybody's portion of frozen Christmas dinner-if everybody lived that long. The humanoids themselves had rejected all terrestrial animal protein, and were putting together a combination of spun vegetable protein that evidently added up to the right balance of amino acids. With the superb a.n.a.lytical laboratories in their noses, they were in no danger of starving.

The Cygnan prisoner, the humanoids had given Jameson to understand, was not just some run-of-the-mill technician, but was an important person they had taken some pains to select. They seemed desperately to want to keep it alive.

The humanoid looking at the stars suddenly bounced into the air and tumbled weightlessly toward Jameson like a giant ball of pink milkweed. Its fluffy tail whipped around the guardrail to anchor it, and it plucked at Jameson's sleeve, making urgent piping sounds. When it finally had Jameson's attention, it struck itself on its little chest and flung a slender arm toward the constellation Cygnus.

"What in the world," Kay said.

"He's telling us where his home is," Jameson said.

"Of course. It would have to be somewhere in the volume of s.p.a.ce between here and Cygnus, along the Cygnans' line of flight. But which star? It might not even be visible to the naked eye."

"It's not Deneb or Albireo. They're too far away from the line of sight toward Cyg X-l, and we know the Cygnans came in more or less under its X-ray umbrella. Wait a minute! I think it's trying to tell me that it's 61 Cygni! But ifthat's so, then-"

Jameson didn't get a chance to finish. Yeh had risen from his seat so abruptly that he had to grasp an armrest to keep from floating off.

"K'an, k'an!" he said excitedly. "Look! It happens!"

In a moment the three of them were crowding the observation rail, looking out into the dark. An awesome event was taking place out there.

Against the burning stars, Jupiter moved!

Jameson could only gape. The scale of what he was witnessing was almost beyond human grasp.

Slowly, ponderously, the colossal bulk of the planet stirred.

It sloshed.

Across its seething face, a great sluggish tidal wave of thickened hydrogen brimmed over hundreds of miles of atmosphere and lapped in an advancing wall that would have tumbled Earth like a cork.

It stretched.

It no longer was the oblate sphere that man had known since he started looking at it through telescopes.

The thing spinning around its waist had given it a flying-saucer shape, a hatbrim of raging hydrogen fighting to pour itself into the circling maw of a gnat.

The gnat had strained and swallowed an elephant. By now, zipping around the captive giant at very nearly the speed of light, the robot probe had converted enough of the stolen hydrogen into Einsteinian ma.s.s to tug at the remainder of that tremendous corpse.

Just how much of Jupiter was left? To Jameson, it looked no smaller than before. Perhaps it had lost a few thousand miles of diameter, perhaps not. As its outer layers were stripped away, the rest of that compressed hydrogen, relieved of pressure, would tend to boil and swell. And even with half its bulk gone, Jupiter would still be the most ma.s.sive object in the solar system other than the Sun itself.

"It won't be there!" Kay said suddenly. "I just realized that from now on when we look up in the sky at night to find Jupiter, it won't be there!"

Jameson looked around and was amazed to see tears running down her cheeks. "Sorry," Kay said. "I'm just tired."

"It'll be our turn someday, Kay," he said. "When we've used up everything else, we'll start using up the planets."

With trembling hands he swung one, of the stubby ship's telescopes around in its gimbals and turned on the magnetic lens. The computer-controlled fields flexed transparent plastic, shaped a pool of mercury into a reflecting curve. A picture stirred itself into being on the photoplastic plate behind the eyepiece, held steady by the electronic image compensator.

A Cygnan ship stretched toward him like a claw. It had stopped rotating. The three long spars, with their buckets of life at the ends, spread motionless from the tip of the notched beam of the drive section. As Jameson watched, the buckets swiveled in their wishbone cradles and snapped into place, reversed. He tried to imagine what was happening inside those worldlets. Had the lakes with their queer bright sailboats been drained? Were the animals hushed in their cages, waiting for gravity to resume?

The spars folded inward, swinging through their fifteen-mile arcs. Jameson could see how their triangular cross sections and the three-sided buckets fit into the grooved sides of the starship, just as Pierce had said they would.

He lifted his face from the eyepiece. Jupiter was picking up momentum, like a stone rolling downhill. It moved past the stars, dragging its moons with it.

And us too, if we don't fire our engines soon, he thought.

He called the observatory and got Maybury. She'd finished her work in the engine room a couple of hours go.

"Are you recording?" he asked.

"Yes, Commander."

"How fast are they accelerating?"

"One gravity, same as before."

"Their trajectory. Is it going to be what we figured?"

In the screen, Maybury bit her lip. "It's too early to tell, Commander."

"Keep tracking them." He switched off.

Kay had returned to her console, taking instrument readings with Yeh and feeding questions to the ship's computer. She looked up as Jameson returned to his seat.

"We're going to have a lot of borrowed momentum when we break loose from Jupiter," she said. "We may reach Earth in less than four months."

Jameson nodded. "The astronomers are going to have a merry time figuring out what all that gravitational displacement will do to the balance of the solar system."

Kay hesitated. "Tod, will... will the Earth be safe?"

Jameson drew a long breath. "We'll know for sure in just a couple of days. That's all the time it will take for them to cross Earth's...o...b..t."

Before returning to his cabin to collapse in his bunk, Jameson sought out Maybury in the observatory.

The ship's engines had been firing steadily for a couple of hours now; Mike and Quent, and the three Chinese fusion techs, were taking turns staying awake to monitor the boron-11 fusion/fission cycle.

Maggie had calculated an escape orbit from the death-grip of Jupiter, which was now falling toward the Sun at more than a thousand kilometers a second. Enough maneuvering jets had been unplugged so that Kay had even been able to put some spin on the ring. The ship would live until it got back to Earth.

Provided Earth was still there.

Maybury looked up from a computer console as he entered. Her face looked dreadful: a wan porcelain mask with two great dark holes in it. Her head moved as though her neck had gone stiff.

"Still working?" he said.

"I thought I'd just set up some hypothetical programs to calculate gravitational stresses for Earth using various trajectories for Jupiter."

"You don't have to stay awake for that. There's not a d.a.m.n thing anybody can do to change things."

"I know. It's just something to do."

He settled down in a seat next to her. With the engines firing, he had almost two pounds of weight.

"I found out where the two humanoids came from."

She was all attention. "Where?"

"61 Cygni."

She nodded slowly. "It could be. It's roughly in the line of flight from Cygnus X-1."

"And it'sclose ."