Louis said, "I didn't know myself till after I was back on Earth. I did some research then."

Both aliens were looking at him. He hadn't really wanted that much of their attention. Oh, well. "It's easy enough to show that the Ringworld is unstable. Stable along the axis, but unstable in the plane. There must have been something to keep the sun on the axis."

"But it's off center now!"

"Whatever it was stopped working."

Chmeee clawed at the invisible floor. "But then they must die! Billions of them, tens of billions-trillions?" He turned to Louis. "I tire of your fatuous smile. Would you talk better without the droud?"

"I can talk fine."

"Talk, then. Why is the Ringworld unstable? Is it not in orbit?"

"No, of course not. It has to be rigid. That terrific spin would pull it rigid. If you nudge the Ringworld off center it'll fall further off center. But the equations are pretty hairy. I played around with a computer and I got numbers I'm not sure I believe."

The Hindmost said, "At one time we thought we might build our own Ringworld. The instability is too great. Even a strong solar flare would exert enough pressure on the structure to throw it off balance. Five years later it would grind against its sun."

"That's the same figure I got," Louis said. "That must be what happened here."

Chmeee was clawing the floor again. "Att.i.tude jets! The Ringworld engineers would have mounted att.i.tude jets!"

"Maybe. We know they had Bussard ramjets. They used them to drive their starships. Okay, a lot of big Bussard ramjets on the rim walls would be enough to keep the Ringworld centered. The motors would fuse the hydrogen in the solar wind. They'd never ran out of fuel."

"We saw nothing. Think how huge the motors would have to be!"

Louis chuckled. "What do you call huge? On the Ringworld? We missed them, that's all." But he couldn't like the way Chmeee stood above him with claws extended.

"You accept it all so easily? There may be enough Ringworld natives to crowd the worlds of known s.p.a.ce thousands of times over. They are more nearly your kind than mine."

"You're a ruthless, merciless carnivore. Try to remember," Louis told the kzin. "Look: it'll bother me. It'll bother me a lot after the Hindmost turns off my droud. But it won't kill me, because I'll be a little bit used to it by then. Can you think of anything we can do to help them? Anything?"

The kzin turned away. "Hindmost, how much time do they have left?"

"I will attempt to find out."

The sun was well off center to the Ringworld. Louis guessed it might be, oh, seventy million miles from the near side, which would put it a hundred and twenty million miles from the far side. The near side would be getting nearly three times as much sunlight as the far side, and the structure rotated in seven and a half thirty-hour days. There would be weather. Plants that couldn't take the changes would be dying. And animals. And men.

The Hindmost had finished its work at the telescope. Now it worked at the computer, out of sight behind the solid green wall. Louis wondered what else was concealed in that hidden part of the ship.

The puppeteer trotted into view. "One year and five months from now, the Ringworld will graze its sun. I expect it will disintegrate then. Given their rotational velocity, the fragments would all recede into interstellar s.p.a.ce."

"Shadow squares," Louis murmured.

"What? Yes, the shadow squares would impact before the sun. Still, we should have at least a year. Plenty of time for us," the Hindmost said briskly. "We will not touch the Ringworld surface at all. Your expedition examined the s.p.a.ceport ledge, from some tens of thousands of miles away, without being fired on by the Ringworld meteor defenses. I believe the s.p.a.ceport has been abandoned. We can land in safety."

Chmeee asked, "What do you expect to find?"

"I'm surprised you haven't remembered." The Hindmost turned to its control board. "Louis, you've had enough time."

"Wait-"

The wire in his brain went dead.

Chapter 5 -.

Withdrawal Symptoms Louis watched through the wall as the puppeteer worked on his droud. He thought of death in mind-stunning numbers, and death as his own very personal experience, and death for aliens who monitored the current to his brain.

Flat heads poised and shifted and nosed the small black casing as if nibbling at a dubious meal. Long tongues and sensitive lips worked inside the casing. In a few minutes the puppeteer had reset the timer to a thirty-hour day, and cut the current by half.

The next day it was pure joy unfiltered by human sense, and nothing could actually bother him, but ... Louis had trouble defining his own feelings. When the current cut off too soon that evening, depression dropped over him like thick saffron smog.

Then Chmeee stooped above Louis Wu, pulled the droud from his scalp, and set it on the stepping disc to be flicked to the flight deck. For resetting. Again.

Louis screamed and leaped. He scrambled up the kzin's broad back via fur handholds and tried to tear his ears off. The kzin whirled. Louis found himself clinging to a great arm, found the arm slinging him across the room. He fetched up against a wall. Half stunned, with blood streaming down his torn arm, Louis turned to the attack.

He turned in time to see Chmeee leap onto the stepping disc just as the Hindmost mouthed the controls.

Chmeee crouched on the black disc, looking dangerous and foolish.

The Hindmost said, "Nothing so ma.s.sive may be flicked to these discs. Do you judge me an idiot, to flick a kzin onto my own flight deck?"

Chmeee snarled, "How much intelligence does it take to sneak up on a leaf?" He flipped the droud to Louis and shambled toward his water bed.

A diversion. Chmeee had s.n.a.t.c.hed the droud from Louis's scalp just after it switched off, solely to drive Louis Wu into berserker rage, to distract the puppeteer's attention.

The Hindmost said, "When next I alter your droud I will do it just before you plug in. Does that make you happy?"

"You know tanj well what makes me happy!" Louis held the droud tightly. It was dead, of course-dead until the timer made it live again.

"You are nearly as long-lived as we are. This is so temporary," the Hindmost wheedled him. "You will be wealthy beyond dreams! The Ringworld s.p.a.cecraft used a method of cheap, large-scale trans.m.u.tation, the same that they must have used to build the Ringworld itself!"

Louis looked up, startled.

"I wish we knew the ma.s.s and bulk of the machine," the puppeteer continued. "The Ringworld s.p.a.cecraft are tremendous things. But we need not transport it. If necessary, a hologram taken by deep-radar, and holograms of the mechanism in action, should be enough to convince my subjects. Then we need only send a General Products #4 craft to pick it up."

The alien would not expect a man deep in current withdrawal to respond to every little comment. Of course not. But from under his brows Louis watched Chmeee, to see how he would handle it.

The kzin was admirable. For a moment he froze. Then, "How did you come to lose your prerogatives?"

"The tale is complex."

"We entered Ringworld system with eleven billion miles to fall and a velocity of fifty-two thousand miles per second to be shed. Only a day has pa.s.sed. We have time."

"So we do, and no other useful work. You must know, then, that Conservative and Experimentalist factions are old among us. Usually the Conservatives rule. But when our world suffered from heat pollution due to too much use of Industrial power, Experimentalists moved our world outward into the cometary halo. An Experimentalist regime altered and then seeded two farming worlds. A later regime moved two more worlds inward from where they had formed as moons of distant ice giants ..."

And Chmeee had gained time to lose his agitation and think what he would say next. Good! Maybe the kzin had earned the position he once held: Speaker-To-Animals, a junior amba.s.sador to humanity.

"... we do the necessary things, then are deposed. It is the general rule. Experimentalists came into power when our probes learned of the Kzinti Empire. I believe Nessus told you how we handled that."

"You aided humanity." Chmeee was peculiarly still. Louis would have expected him to be tearing up the walls. "The four Wars With Men killed four generations of our mightiest fighters so that the more docile among us might reproduce their kind."

"We hoped you would become able to deal amicably with other species. My faction also established a trading empire in this region. Despite our successes, we were losing our authority. Then it was discovered that the core of our galaxy has exploded. The shock wave will arrive in twenty thousand years. Our faction stayed in power, to arrange the exodus of the Fleet of Worlds."

"How fortunate for you. Yet they deposed you after all."

"Yes."

"Why?"

The puppeteer didn't answer for a time. Then: "Some of my decisions were not popular. I meddled with human and kzinti destiny. Somehow you learned our secret, how we had tampered with the Fertility Laws on Earth in an attempt to breed lucky humans, and with the course of the First War With Men, to produce reasonable kzinti. My predecessor established General Products, the interstellar trading empire. It was said that he had made a virtue of madness, since only the mad among us will risk their lives in s.p.a.ce. When I arranged your expedition to explore the Ringworld, I was called mad, to risk contact with so advanced a technology. But one does not hide one's sight from danger!"

"So they deposed you."

"It may have been ... a convenient excuse." The Hindmost paced restlessly: clopclopclop, clopclopclop. "You know that I agreed to take Nessus as mate if he returned from the Ringworld. He demanded this concession. And he returned, and we mated. Then we did it again, for love. Nessus was mad, and the Hindmost has often been mad, and ... they deposed me."

Louis suddenly asked, "Which of you is male?"

"I wonder why you did not ask that of Nessus. But he would not have told you, would he? Nessus is shy on certain subjects. We have two kinds of male, Louis. My kind implants its sperm in the female's flesh, and Nessus's kind implants its egg in the female with a most similar organ."

Chmeee asked, "You have three sets of genes?"

"No, two only. The female contributes none. In fact, females mate among themselves in another way to make more females. They are not properly of our species, though they have been symbiotic with us for all history."

Louis winced. The puppeteers bred like digger wasps: their progeny ate the flesh of a helpless host. Nessus had refused to talk about s.e.x. Nessus was right. This was ugly.

"I was right," said the Hindmost. "I was right to send a mission to the Ringworld, and we will prove it. Five days in, and no more than ten on the s.p.a.ceport ledges, and five more to reach flat s.p.a.ce where we may escape by hyperdrive. We need never board the Ringworld at all. Halrloprillalar told Nessus that the Ringworld ships carried lead, for compactness, and trans.m.u.ted it into air and water and fuel during the journey. A Conservative government could not deal with the ramifications of such a technology. They will reinstate me."

Current-withdrawal depression left Louis no urge to laugh. Still, it was all very funny, and funnier still because it was his own fault from the beginning.

The next morning the aliens cut the droud's current flow in half again, and left it alone thereafter. It shouldn't have made that much difference. Under the wire he was still content. But for years he had suffered through the depression when the timer stopped, knowing what he would feel when the current resumed. His depressions were worse now, and there was no security. The aliens could cut the current at any time ... and even if they didn't, he would still have to give it up.

What the aliens talked about during those four days he didn't know. He tried to concentrate on the ecstasy in the wire. Vaguely he remembered them calling up holograms from the computer. There were the faces of Ringworld natives: the small ones completely covered with golden hair (and one, a priest, was shaven); and the tremendous wire sculpture in the sky castle (stub of a nose, bald head, knife-slash lips); and Halrloprillalar (probably of the same race); and Seeker, the wanderer who had taken Teela under his protection (almost human, but muscled like a Jinxian, and beardless). There were cities ruined by time and by floating buildings that had fallen when their power died. There were holograms of Liar's approach to a shadow square, and of a city nestled in a smoke cloud of fallen shadow-square wire.

The sun grew from a point to a black dot with a bright rim around it, its brightness blocked by flare shielding on Needle's inner hull. The blue halo around the sun expanded.

In dreams Louis returned to the Ringworld. In a great floating prison he hung head down from his burned-out flycycle, ninety feet above a hard floor strewn with the bones of earlier captives. Nessus's voice beat in his ears, promising rescue that never came.

When awake he took refuge in routine ... until on the evening of the fourth day he looked at his dinner, then dumped it and dialed for bread and a selection of cheeses. Four days to realize that he was forever beyond the reach of the ARM. He could eat cheese again!

What's good besides the wire? Louis asked himself. Cheese. Sleeping plates. Love (impractical). Wild skin dye jobs. Freedom, security, self-respect. Winning as opposed to losing. Tanj, I've almost forgotten how to think like this, and I've lost it all. Freedom, security, self-respect. A little patience and I can take the first step. What else is good? Brandy poured in coffee. Movies.

Twenty-three years earlier, Speaker-To-Animals had brought the s.p.a.cecraft Lying b.a.s.t.a.r.d close to the Ringworld's edge. Now Chmeee and the Hindmost watched recordings of that event.

Seen from that close, the Ringworld became straight lines meeting at a vanishing point. From out of the point where the checkered blue inner surface dropped to meet the top and bottom edges of the rim wall, the rings of the s.p.a.cecraft decelerator system seemed to fly straight into the camera, over and over, in infrared and visible and ultraviolet light and deep-radar images. Or they crept past in slow motion, huge electromagnets, all identical.

But Louis Wu watched the entire eight hours of the Changeling Earth fantasy epic while getting soddenly drunk. Brandy in coffee, then brandy and soda, then brandy alone. It was a movie he watched, not a sensual: it used live actors and only two of the human senses. He was at two removes from reality.

At one point he tried to engage Chmeee in a discussion of Saberhagen's use of impossible visual effects. He retained just enough wit to desist at once. He dared not talk to Chmeee while drunk. The puppeteers have hidden ears, hidden ears -- The Ringworld grew large.

For two days it had been a finely etched blue ring, narrow, flimsy-looking, off center to its sun, growing as the black circle of its sun grew. Gross detail appeared. An inner ring of black rectangles, the shadow squares. A rim wall, a mere thousand miles high, but growing to block their view of the Ringworld's inner surface. By evening of the fifth day Hot Needle of Inquiry had lost most of its velocity, and the rim wall was a great black wall across the stars.

Louis was not under the wire. Today he'd forced himself to skip it; and then the Hindmost had told him that he would send no current until they had landed safely. Louis had shrugged. Soon, now- "The sun is flaring," the Hindmost said.

Louis looked up. Meteor shielding blocked the sun. He saw only the solar corona, a circle of flame enclosing a black disc. "Give us a picture," he said.

Darkened and expanded in the rectangular "window," the sun became a huge, patterned disc. This sun was slightly smaller and cooler than Sol. There were no sunspots, no blemishes, except for a patch of glaring brightness at the center. "Our vantage is not good," the Hindmost said. "We see the flare head on."

Chmeee said, "Perhaps the sun has become unstable recently. This could explain why the Ringworld is off center."

"It may be. Lying b.a.s.t.a.r.d's records show a flare during your approach to the Ringworld, but for most of that year the sun was quiet." The Hindmost's heads poised above his instrument board. "Odd. The magnetic patterns-"

The black disc slid behind the black edge of the rim wall.

"The magnetic patterns of that star are most unusual," the Hindmost continued.

Louis said, "So go back for another look."

"Our mission does not permit the collection of random data."

"No curiosity?"

"No."

From under ten thousand miles away, the black wall seemed straight as a ruled line. Darkness and speed blurred all detail. The Hindmost had the telescope screen set for infrared light, but it did little good ... or did it? There were shadows along the bottom of the rim wall, triangles of coolness thirty to forty miles tall, as if something on the inner side of the thousand-mile-high wall was reflecting sunlight away. And here came a darker, cooler line along the bottom, moving left to right.

Chmeee asked politely, "Are we boarding or merely hovering?"

"Hovering, to a.s.sess the situation."

"The treasure is yours. You may leave without it if it pleases you."

The Hindmost was restless. His legs gripped the pilot's bench hard. Muscles twitched in his back. Chmeee was relaxed; he seemed pleased with himself. He said, "Nessus had a kzin for his pilot. There were times when he could give way to total fear. You dare not. Can the automatics land Needle for you while you hide in stasis?"

"What if an emergency developed? No. I did not antic.i.p.ate this."

"You must land us yourself. Do it, Hindmost."

Needle turned nose down and accelerated.

It took nearly two hours to accelerate to the Ringworld's seven hundred and seventy miles per second. By then, hundreds of thousands of miles of the dark line had raced past them. The Hindmost began to ease them closer-slowly, so slowly that Louis wondered if he would back out. He watched without impatience. He wasn't under the wire, and by his own choice. Nothing else could be that important.

But where was Chmeee's patience coming from? Was Chmeee feeling his oncoming youth? A human reaching his first century could feel that he had all the time in the world, for anything. Would a kzin react that way? Or ... Chmeee was a trained diplomat. Perhaps he could hide his feelings.