Louis had thought this through, over and over, while under the wire. He tried to remember the optimism he'd felt then, but it was gone. "We stall. We search the s.p.a.ceport ledges. When we don't find anything, we search the Ringworld itself. We're equipped for that. We don't let the Hindmost give up till we find our own answer. Whatever it might be."

"This situation is entirely your fault."

"I know. That's what makes it so funny."

"Laugh, then."

"Give me my droud and I'll laugh."

"Your foolish speculations have left us slave to a mad root-eater. Must you always pretend to more knowledge than is yours?"

Louis sat down with his back to a yellow-glowing wall. "It seemed so reasonable. Tanj, it was reasonable, Look: the puppeteers were studying the Ringworld years before we came on the scene. They knew its spin and its size and its ma.s.s, which is just more than the ma.s.s of Jupiter. And there's nothing else in the system. Every planet, every moon, every asteroid, gone. It seemed so obvious. The Ringworld engineers took a Jupiter-style planet and made it into building materials, and they used the rest of the planetary garbage, too, and they built it all into a Ringworld. The ma.s.s of, say, Sol system would be just about right."

"It was only speculation."

"I convinced you both. Remember that. And gas giant planets," Louis continued doggedly, "are mostly hydrogen. The Ringworld engineers would have had to convert hydrogen into Ringworld floor material -- whatever that stuff is; it's like nothing we ever built. They would have had to trans.m.u.te material at a rate that would outstrip a supernova. Listen, Chmeee, I'd seen the Ringworld. I was ready to believe anything."

"And so was Nessus." The kzin snorted, forgetting that he too had believed. "And Nessus asked Halrloprillalar about trans.m.u.tation. And she thought our two-headed companion was charmingly gullible. She told him a tale of Ringworld starships carrying lead to trans.m.u.te into fuel. Lead! Why not iron? Iron would bulk more, but its structural strength would be greater."

Louis laughed. "She didn't think of it."

"Did you ever tell her that trans.m.u.tation was your hypothesis?"

"What do you think? She'd have laughed herself to death. And it was too late to tell Nessus. By then Nessus was in the autodoc with one head missing."

"Uurrr."

Louis rubbed his aching shoulders. "One of us should have known better. I told you I did some math after we got back. Do you know how much energy it takes to spin the ma.s.s of the Ringworld up to seven hundred and seventy miles per second?"

"Why do you ask?"

"It takes a lot. Thousands of times the yearly energy output of this kind of sun. Where would the Ringworld engineers get all that energy? What they had to do was disa.s.semble a dozen Jupiters, or a superjovian planet a dozen times Jupiter's ma.s.s. All mostly hydrogen, remember. They'd use some of the hydrogen in fusion for the energy to run that project, and reserve more of it in magnetic bottles. After they made the Ringworld from the solid residues, they'd have fuel for fusion rockets to spin it up to speed."

"Hindsight is so wonderful." Chmeee prowled back and forth along the corridor, on his hind legs, like a man, deep in thought. "So we are slaved to a mad alien searching for a magical machine that never was. What do you hope will happen in the year left to us?"

It was difficult to be optimistic without current. "We explore. Trans.m.u.tation or not, there's got to be something valuable on the Ringworld. Maybe we'll find it. Maybe there's a United Nations ship already here. Maybe well find a thousand-year-old Ringworld s.p.a.ceship crew. Maybe the Hindmost will get lonely and let us join him on the flight deck."

The kzin paced, his tail switching back and forth. "Can I trust you? The Hindmost controls the current flow to your brain."

"I'll kick the habit."

The kzin snorted.

"Finagle's festering t.e.s.t.i.c.l.es! Chmeee, I'm two and a quarter centuries old. I've been everything. I've been a master chef. I helped build and operate a wheel city above Down. I settled on Home for a while and lived like a colonist. Now I'm a wirehead. Nothing lasts. You can't do any one thing for two hundred years. A marriage, a career, a hobby-they're good for twenty years, and maybe you go through a phase more than once. I did some experimental medicine. I wrote a big chunk of that doc.u.mentary on the Trinoc culture that won a-"

"Current addiction involves the brain directly. It's different, Louis."

"Yeah. Yeah, it's different." Louis felt the depression like a wall of black jelly sagging inward, crushing him down. "It's all black or all white. The wire is sending or it isn't. There's no variety. I'm sick of it. I was sick of it before the Hindmost took over my current flow."

"But you did not give up the droud."

"I want the Hindmost to think I can't."

"You want me to think you can."

"Yeah."

"What of the Hindmost? Never have I heard of a puppeteer who behaved so strangely."

"I know. It makes me wonder if all the mad traders were Nessus's s.e.x. If the ... call them sperm-carrying males ... are the dominant ones."

"Urrr-"

"It doesn't have to be that way. The kind of madness that sends a puppeteer to Earth because he can't deal with other puppeteers, that's not the same as the madness that makes a Joseph Stalin. What do you want from me, Chmeee? I don't know how he'll act. If we give him some credit for brains, then he'll use General Products trading techniques. It's the only way he knows to deal with us."

The canned air tasted cool and metallic. There was too much metal in these ships, Louis thought. It seemed queer that Halrloprillalar's people hadn't used more advanced materials. Making a Bussard ramjet was no task for primitives.

The air smelled funny, and the yellow-white glow in the walls dimmed and brightened irregularly. Best get back to their pressure suits, soon.

Chmeee said, "There is the lander. It would function as a s.p.a.cecraft."

"What do you call a s.p.a.cecraft? It must have interplanetary capability. It'd need that to get around on the Ringworld. I wouldn't think we could reach another star with it."

"I was thinking of ramming Needle. If there is no escape, we may take vengeance."

"That'll be fun to watch. You ramming a General Products hull."

The kzin loomed over him. "Do not be too amusing, Louis. What would I be on the Ringworld, with no mate, no land, no name, and a year to live?"

"We'd be buying time. Time to find a way off. In the meantime"-Louis stood up-"officially, we're still searching for a magic trans.m.u.tation machine. Let's make at least a token search."

Chapter 7 -.

Decision Point Louis woke ravenous. He dialed a cheddar cheese souffl' and Irish coffee and blood-oranges and ate his way through it all.

Chmeee slept curled protectively around himself. He looked different somehow. Neater-yes, neater, because the scar tissue under his fur had disappeared and the new fur was growing out.

His stamina was impressive. They had searched every one of the four Ringworlder ships, then moved on to a long, narrow building at the very lip of infinity, which proved to be the guidance center for the s.p.a.cecraft accelerator system. At the last, Louis was moving in a fog of exhaustion. He knew he should have been examining Needle for details of construction, weak points, routes into the flight deck. Instead he had watched Chmeee, with hatred. The kzin never stopped to rest.

The Hindmost appeared from somewhere, from behind or within the green-painted private sector. His mane was combed and fluffy, dressed with crystals that changed their spectral color as he moved. Louis was intrigued. The puppeteer had been scruffy while he was flying Needle alone. Did he dress to impress his alien prisoners with his elegance?

He asked, "Louis, do you want the droud?"

Louis did, but-"Not yet."

"You slept eleven hours."

"Maybe I'm adjusting to Ringworld time. Did you get anything done?"

"I took laser spectrograms of the ships' hulls. They are largely iron alloys. I have deep-radar scans, two views each for the four ships; I moved Needle while you slept. There are two more s.p.a.ceport ledges one hundred and twenty degrees around the Ringworld. I located eleven more ships by their hull composition. I could not learn detail at this distance."

Chmeee woke, stretched, and joined Louis at the transparent wall. "We learn only to ask more questions," he said. "One ship was left intact, three were stripped. Why?"

"Perhaps Halrloprillalar could have told us," the Hindmost aid. "Let us deal with the only urgent question. Where is the trans.m.u.tation device?"

"We have no instruments here. Flick us to the lander, Hindmost. We will use the screens on the flight deck."

Eight screens glowed around the horseshoe curve of the lander's instrument board. Chmeee and Louis studied ghostly schematics of the Bussard ramjet ships, generated by the computer from the deep-radar scans.

"It looks to me," Louis said, "like one team did the entire looting job. They had three ships to work with, and they took what they wanted most first. They kept working till something stopped them: they ran out of air or something. The fourth ship came later. Mmm ... but why didn't the fourth crew loot their own ship?"

"Trivialities. We seek only the trans.m.u.ter. Where is it?"

Chmeee said, "We could not identify it."

Louis studied the deep-radar ghosts of four ships. "Let's be methodical. What isn't a trans.m.u.tation system?" He traced lines on the image of the one intact ship, using a light-pointer. "Here, these paired toroids circling the hull have to be the ramscoop field generators. Fuel tanks here. Access tubes here, here, here ..." As he pointed them out, the. Hindmost obliged by removing sections of ship from the screen. "Fusion reaction motor, this whole section. Motors for the landIng legs. Take out the legs too. Att.i.tude jets here, here, here, all fed by tubes along here carrying plasma from the one small fusion generator, here. Battery. This thing with the snout, pointing out of the middle of the hull-what did Prill call it?"

"Cziltang brone," Chmeee sneezed. "It softens the Ringworld floor material temporarily, for penetration. They used it instead of airlocks."

"Right." Louis continued, with enthusiasm and hidden glee. "Now, they probably wouldn't keep the magic trans.m.u.ter in the living quarters, but ... sleeping rooms here, control rooms here, here, here, the kitchen-"

"Could that be-"

"No, we thought of that. It's just an automated chemistry lab."

"Proceed."

"Garden area here. Sewage treatment feeds in. Airlocks ..."

When Louis had finished, the ship was gone from the screen. The Hindmost patiently restored it. "What did we overlook? Even if the trans.m.u.ter was dismounted, removed, there would be s.p.a.ce for it."

This was getting to be fun. "Hey, if they really kept their fuel outside-lead, molded around the hull-then this isn't really an inboard hydrogen tank, Is it? Maybe they kept the magic trans.m.u.ter in them. It needed heavy padding or heavy insulation ... or cooling by liquid hydrogen."

Chmeee asked, before the Hindmost could, "How would they remove it?"

"Maybe with the cziltang brone from another ship. Were all the fuel tanks empty?" He looked at the ghosts of the other ships. "Yeah. Okay, we'll find the trans.m.u.ters on the Ringworld ... and they won't be working. The plague will have got to them."

"Halrloprillalar's tale of the bacterium that eats superconductor is in our records," the Hindmost said.

"Well, she really couldn't tell us an that much," said Louis. "Her ship left on a long tour. When it came back, there was no more Ringworld civilization. Everything that used superconductors had stopped." He had wondered how much to believe of Prill's tale of the Fall of the Cities. But something had destroyed the Ringworld's ruling civilization. "Superconductor is almost too wonderful. You end up using it in everything."

"Then we can repair the trans.m.u.ters," said the Hindmost.

"Oh?"

"You will find superconducting wire and fabric stored aboard the lander. It is not the same superconductor the Ringworld used. The bacterium will not touch it. I thought we might need trade goods."

Louis kept his poker face intact, but the Hindmost had made a startling statement. How did puppeteers come to know so much about a mutant plague that killed Ringworld machines? Suddenly Louis didn't doubt the bacterium at all.

Chmeee hadn't caught it. "We want to know what the thieves used for transportation. If the rim-wall transport system failed, then our trans.m.u.ters may be just the other side of the rim wall, abandoned there because they stopped working."

Louis nodded. "Failing that, we've got a lot of territory to search. I think we should be looking for a Repair Center."

"Louis?"

"There has to be a control and maintenance center somewhere. The Ringworld can't run itself forever. There's meteor defense, meteor repair, the att.i.tude jets ... the ecology could go haywire-it all has to be watched. Of course the Repair Center could be anywhere. But it's got to be big. We shouldn't have that much trouble finding it. And we'll probably find that it's been abandoned, because if anyone had been minding the store, he wouldn't have let the Ringworld slide off center."

The Hindmost said, "You have been putting your mind to this."

"We didn't do too well the first time we came here. We came to explore, remember? Some kind of laser weapon shot us down, and we spent the rest of our time trying to get off alive. We covered maybe a fifth of the width, and learned just about nothing. It's the Repair Center we should have been looking for. That's where the miracles are."

"I had not expected such ambition from a current addict."

"We'll start cautiously." Cautiously for humans, Louis told himself; not for puppeteers. "Chmeee's right: the machines could have been dumped as soon as they were through the rim wall, when the bacterium got to them."

Chmeee said, "We should not try to take the lander through the rim wall. I have no faith in an alien machine a thousand years old. We must go over."

The Hindmost asked, "How would you avoid the meteor defense?"

"We must try to outguess it. Louis, do you still believe that what fired on us was merely an automated defense against meteors?"

"I thought so at the time. It all happened so tanj fast!" Falling sunward, all a little edgy, daunted by the reality of the Ringworld. All but Teela, of course. A momentary flash of violet-white; then Liar was embedded in tenuous violet-glowing gas. Teela had looked out through the hull. "The wing's gone," she'd said.

"It didn't fire on us till we were on a course to intersect the Ringworld surface. It's got to be automated. I told you why I think there's n.o.body in the Repair Center."

"n.o.body to fire on us deliberately. Very well, Louis. Automatics would not be set to fire on the rim transport system, would they?"

"Chmeee, we don't know who built the rim transport system. Maybe it wasn't the Ringworld engineers; maybe it was added later, by Prill's people-"

"It was," said the Hindmost.

His crew turned to look at the puppeteer's image on the screen.

"Did I tell you that I spent some time at the telescope? I have learned that the rim transport system is only partly finished. It runs along 40 percent of this rim wall, and does not include the section we occupy now. On the portward rim wall the system is only 15 percent complete. The Ringworld engineers would not have left so minor a subsystem half built, would they? Their own mode of transport may have been the same s.p.a.cecraft used to supervise construction."

"Prill's people came later," Louis said. "Maybe a lot later. Maybe the rim transport system got too expensive. Maybe they never actually completed their conquest of the Ringworld ... but then why were they building starships? Oh, futz, we may never know. Where does this leave us?"

"It leaves us trying to out-think the meteor defense," Chmeee said.

"Yeah. And you were right. If the meteor defense made a habit of firing on the rim wall, n.o.body would have built anything there." Louis chewed it a moment longer. There would be holes in his a.s.sumptions ... but the alternative was to go through the wall via an ancient cziltang brone of unknown dependability. "Okay. We fly over the rim wall."

The puppeteer said, "You suggest a fearful risk. I prepared as best I could, but I was forced to use human technology. Suppose the lander should fail? I hesitate to risk any of my resources. You would be stranded. The Ringworld is doomed."