They had heard of such. They didn't quite believe and they didn't quite disbelieve.

  Louis drew in the mud: Homo habilis, life size, as best he could render him. "Pak breeder. Our ancestors lived on a planet like the world I was born on, a ball, but much closer to the center of our whorl of stars," and he drew a barred spiral, the galaxy. "We're out here. The Pak lived in there." He couldn't draw the Pak world. Nobody had ever seen it. "A plant grew there called 'tree-of-life.'"

  He began to alter Homo habilis, giving him a swollen misshapen head, swollen joints, wrinkled and folded skin, toothless jawbones grown through the gums into a bony beak.

  "You're turning from children into adults," he told them. "When all humans were alike, before there was a Ringworld, there were children, and adults to make more children, and a third shape to protect them both. Adults didn't have minds then. When an adult got old enough he would eat tree-of-life --"

  "She," Parald said, and giggled.

  Stet, their generic pronoun was female. Louis said, "Then she would sleep, and change as she slept, like a butterfly. Her sex would fade away. Protector men and women look alike. Her jaw would grow to replace her teeth, her brain case would expand, her joints would expand to give the muscles greater leverage, her skin would become thick leather armor. When the change was over, she would be smarter and stronger, and she would care for nothing except to protect her children. Protectors fought terrible wars over whose children would survive."

  Strill asked, "Why doesn't it happen to us?"

  "There's an element almost missing from the soil beneath the Arch. The virus that makes protectors can't live without it. But in a cavern under one of the islands on the GreatOcean, tree-of-life still grows with the virus in the root.

  "The terrible thing about a protector is that she'll do anything to give an edge to her own relatives. Whoever built the Ringworld locked the tree-of-life up so nobody could reach it. It grows in artificial light in great plantations beneath the Map of Mars. But somebody must have got to it --"

  "That's what scares the Web Dweller!" Parald crowed.

  "Right. He thinks he's found a protector on the other GreatOcean, and another halfway up the Arch to antispin, and maybe more at work on the rim wall. The Web Dweller isn't related to any human protector. By instinct they would call him an enemy. He controls the Meteor Defense in the RepairCenter. With that he can burn whatever he likes, anywhere on the Arch.

  "So who should we be afraid of? The Web Dweller or the protectors?"

  The children shivered, and giggled, and then began to talk.

  Louis listened and learned. They knew of protectors. War was only a rumor to them, yet the rumor came clothed in protector-shaped armor. All hominids seemed to carry that shape in their minds, as heroes or monsters, as Saint George or Grendel; as designs for armor among the Grass Giants and as pressure suits on the spaceport ledge.

  After much argument, the children seemed to side with the Hindmost. Strangers didn't compete, didn't steal, didn't rape; and what could be stranger than the Web Dweller?

  Presently they all ran off to swim in the lake.

  ***

  Plants here reminded Louis of another plant with a fat root like a beet. He began digging. Sawur watched for a bit, then asked, "Well, Luweewu, can you feed yourself?"

  "I think so. It isn't the style of life whereby a man gets fat," he sad.

  "And are you glad you came among us?"

  "Oh, yes." He was barely listening. A decision he'd made eleven years ago was unraveling.

  "But you wanted Strill."

  Louis sighed. Strill would have been a delight, but even Sawur, mature at forty-odd Earth year, was as close as he wanted to get to child molesting.

  He said, "Strill is beautiful. Sawur, if Strill had come, it would have been bad news. I can tell how wealthy a culture is from the woman who shares her tent with me. I'm the prize here, whatever my real value --"

  "High."

  "-- and you claimed me. But if people are starving, or beset by predators, or at war, they try to guess what prize I want. Then I find some glorious young woman in my bed and I know we have a problem."

  "But *you* would not."

  "No, I mean they might need more than ideas." He'd given away two of his cargo plates to people along the river who needed heavy lifting power. He didn't want to tell Sawur that, so he only said, "Knowledge is like rishathra. You have it, you give it away, you still have it. But I've had to give away tools."

  "What made you so twitchy this morning? Protectors?"

  Louis dropped a root into his pack. Now he had four. "You know about protectors?"

  "Since I was a little girl. In the stories they are heroes, but at the end of time their battles destroy Arch and world together. Kidada and I don't tell those stories anymore."

  "These are heroes," Louis agreed. "The ones on the rim wall, they're repairing motors that hold the Arch where it belongs. Another has been repelling invaders. But protectors can be a bad thing. The Web Dweller's records suggest that protectors destroyed all the life on Home, on one of our ball worlds. It was part of a war between protectors who wanted more turf for their breeders."

  Sawur asked, "Do you trust the Web Dweller's records?"

  "They're very good."

  "Shall we swim?"

  ***

  In mid-afternoon the boys killed something like a small antelope. The children cut a pole to carry it down to the village, with Louis marching at the fore end. It was pleasant to be the strongest man, and not all that uncommon. The average Ringworld hominid was smaller than Louis Wu.

  The Swimmers had moved on, but the Sailors and their ship were still in port. They'd caught a few fish and started the fire. By halfnight the antelope was nearly done.

  Half seen between the huts, tonight the window in the cliff showed the Ringworld edge-to-edge, a checked blue and white band with black sky along either edge.

  Where in tanj were the fearless vampire hunters?

  Louis set his assortment of roots to roast at the edge of the coals. Children and adults were abuzz with questions.

  "It's the Arch," he told them. "Tonight the Web Dweller must be looking all the way across to the opposite edge. See, there's the edge of the sun itself, and that's part of one of the shadow squares that hide the sun at night. All that patchy white is clouds. No, you can't see them moving. If they moved as fast as that, the wind would blow the landscape right off the scrith foundation! Those glittering dots and curves and lines, if you can make them out, those are seas and rivers."

  "He's showing the stars larger, too" old Kidada said. "What's that moving one? And, Louis, what is the Web Dweller trying to tell you?"

  Off the edges of the Arch, all of the bright stars were adrift. The brightest was moving crosswise to the rest. Louis had been watching it. It slowed as it approached the rim wall. It was on the rim wall, turning a stretch of the rim into a brilliant blue-white line ... and it went out.

  Louis said, "He's trying to tell me that another invader has come under the Arch."

  Parald sliced off meat and passed it to Kidada, then Sawur, then a sudden crowd. Wheek offered Louis a fish on a stick. Weavers and Sailors took their meals and moved through the huts to the cliff side.

  *I show you the Ringworld invaded; come and talk. I do not show you Valavirgillin alive or dead; you must ask.*

  Louis accepted a slice of antelope and, eating two-handed, followed Parald.

  The Weavers sat on tables and the sand, watching. Sawur made room for him on a table.

  Within the webeye window, a shadow square crossed the sun. Details became clearer, sharper.

  Brilliant light flared on the rim wall. Over the next several minutes the poin
t moved inward, above the Ringworld surface; dimmed; blurred; went out.

  Dull stuff, but they watched. Louis wondered if Weavers would become addicted to passive entertainment.

  The clouds were moving now. Vast wind patterns showed their shapes in fast-forward. A tiny pale hourglass sucked streamlines at both ends: a hurricane on its side, a meteor puncture hole.

  Fast-forward, a solar prominence rose past the rim of the shadow square. A shock wave of green brilliance rose up the plume. Then a burning green star delicately touched the rim wall at the point where the earlier star had rested. The green star walked off the rim and blurred as it intersected clouds.

  As the last sliver of sun vanished overhead, the Weavers all streamed off to their huts, chattering in excitement punctuated by yawns. Louis watched in astonishment. These Weavers were *really* diurnal.

  Before the Hindmost could decide to speak in front of them, Louis strolled back to the fire. He raked two roots out of the coals.

  One was acrid. One wasn't bad. He didn't always eat this well.

  The Sailors had remained. One came to join him. "That show is for you, isn't it?"

  Louis looked back. Within the Hindmost's window, the green star had gone out.

  "I don't know what to say to him," Louis said. "Wheek, did he speak to you?"

  "No. He frightens me."

  The Hindmost's message seemed clear enough. Fusion drive: invading spacecraft. ARM and Patriarchy and the Fleet of Worlds all knew of the Ringworld. Each had had time to mount expeditions. Or the invader might be a returning City Builder craft, or someone else entirely.

  The automatic Meteor Defense wouldn't react if an invader moved slowly. Some entity was actively killing ships.

  The killer had a problem, too. Lightspeed. The invader had landed light-minutes from the second GreatOcean, but the attack had come hours slow. A solar plume must be ejected, the superthermal. laser effect must propagate along the plasma, and it all took time; but there was still that lightspeed delay. The prey might still escape.

  The Hindmost would be *extremely* eager to find a hyperdrive ship undamaged.

  Low music was playing through distant branches. Wheek had gone to his boat. Louis raked a third root from the fire. He slit it, then pushed on the ends to open it. Live steam, and a smell not too different from a sweet potato.

  He wondered if he'd found wild tree-of-life. No matter. The soil wouldn't have enough thallium; the plant wouldn't support the virus that caused the change; and cooking would kill it anyway. Louis took his time eating, then went toward Sawur's wicker hut.

  The music seemed to grow louder. Strange stuff, with qualities of wind and humming strings. He stopped outside Sawur's wicker hut to listen.

  The music stopped. A voice said, "Will you not speak to the Web Dweller?"

  "Not tonight," Louis said, and looked around him. The voice was a child's, with a bit of a speech impediment. Tonight was foggy, but Ringworld nights were bright, and he should have seen *something*, Louis thought.

  "Will you show yourself?"

  A nightmare rose out of low brush, too near. Lank hair covered its body, the color of the night. Big spade teeth forced an exaggerated grin. Long arms, big hands; a miniature harp in one hand.

  The Ghoul seemed male, but a kilt hid that. Sparse facial hair, flat chest: a child, boy or girt.

  "Nice kilt," Louis said.

  "Nice backpouch. Weaver work is loved all through the ShenthyRiver valley."

  Louis knew that: he had seen Weaver work tens of thousands of miles downstream. He asked, "Do you do security work for the Weavers?"

  "Sec...?"

  "Guard their possessions by night."

  "Yes, we stop thieves."

  "But you're not paid for normal, ah ..."

  In lieu of answer -- *was* there a word for garbage disposal plus funeral service? -- the child blew into the handle of his harp while his fingers played across the holes and tweaked the strings. He played a tune on his tootling, twanging instrument, then held it out. "Do you have a name for this?"

  "Illegitimate child of a harp and a kazoo. A kazarp?"

  "Then I am Kazarp," the Ghoul said. "Are you Louis Wu?"

  "*How* --"

  "We know that you boiled an ocean, far up the Arch --" Kazarp pointed. "-- *there*. You vanish for forty-one falans, and we find you here."

  "Kazarp, your communications are awesome. How is it done?" Louis didn't expect an answer. Ghouls had their secrets.

  "Sunlight and mirrors," Kazarp said. "Was the Web Dweller your friend once?"

  "Ally. Not friend. It's complicated."

  The pointy-faced hominid examined Louis. Louis was trying to ignore the smell of a carrion eater's breath. The child asked, "Would you have spoken to father?"

  "Maybe. How old are you?"

  "Near forty falans."

  Ten years. "How old is your father?"

  "A hundred fifty."

  "In falans I'm about a thousand," Louis Wu said. He decided that the child was too easy to notice. A distraction? Was his father eavesdropping?

  Well, then, how to tell this? Should he? Louis said, "The Web Dweller, the big cat, two City Builders, and me. We saved everything under the Arch."

  Kazarp said nothing. Some wanderers must be great liars, Louis thought. He said, "We had a plan. But it would kill s-s-some ... it would kill *many* of the people we were trying to save. I'm as guilty as I thought the Web Dweller was, and I hated him for it. Now I find out that the Web Dweller saved many more than I realized."

  "Then you must thank him. And apologize?"

  "I did that, Kazarp. Kazarp, I expect we'll talk again, but my species needs sleep. If your father wants to talk, a Ghoul could certainly find me." Louis knelt to enter the wicker house.

  "Did it leave a bad taste?"

  Louis laughed. A Ghoul might well know all about bad taste! *But that voice wasn't Kazarp.*

  He stepped back outside. He said, "Yes."

  "Still, you swallowed what you must. Now the Web Dweller must decide. A valuable alliance, a breach of manners -- you're a thousand falans old? How old is the Web Dweller?"

  "Even guessing makes my head hurt."

  The child had settled cross-legged and was playing background music to the voice that spoke from nowhere. The adult's voice said, "We live perhaps two hundred falans. If your misunderstanding only cost you forty or fifty falans, for such as you it must be worth repairing."

  "Oh, the City Builders were refugees, and killing doesn't bother Chmeee! But *I'm* still guilty. I consented. I thought we killed all those people to save the rest."

  "Be joyful."

  "Yeah." He couldn't ask even a Ghoul to consider the numbers involved. No sane mind could grasp them. *Hominids of varying intelligence inhabit the Ringworld, invading every conceivable ecological niche. Cattle, otters, vampire bats, hyenas, hawks ... Roughly thirty trillion, with a margin of error bigger than all known space.*

  *We can save most of them. We will generate a solar flare and turn it on the Ringworld surface to bring heated hydrogen fuel to the few remounted attitude jets on the rim walls. Lose fifteen hundred billion to radiation and fire. They would die anyway. Save twenty times as many.*

  But the Hindmost's advanced, adaptable programs had exercised fine control over a plasma jet bigger than worlds. The Hindmost *had not* killed fifteen hundred billion. Not at all.

  But Louis Wu had consented to their deaths.

  He said, "That region of the RepairCenter was infested with tree-of-life ... with the plant that changes hominids into something very different. Kazarp says you're about the right age to become a protector. I'm seven times that old. The virus in t
ree-of-life would kill old Louis Wu.

  "So I sent the Web Dweller in alone to cause their deaths. Otherwise I would have seen how many didn't die. I took all those lives, and the only apology I could make was to die."

  "But you're not dead," the hidden voice said.

  "Dying. With the medkit on my cargo plates, I might get as much as another falan."

  The child's music broke in discord, and the night was silent.

  Tanj! He had longevity and he'd thrown it away, but these people had never had the choice. Just how ill-mannered had he been?

  The adult said, "And you gave up his friendship."

  "The Web Dweller doesn't exactly have friends. He bargains very exactly, and his aim is always to make himself safer. He intends to live forever, whatever that takes. That bothered me then. It bothers me now. What will it take?"

  "Your alliance? Does he have something to gain from you?"

  "A traveling pair of hands. A life to risk that isn't his own. A second opinion. He can offer me another hundred twenty falans of life." And that was scary.

  "Could he do that for, let us say, me?"

  Offer longevity to a Ghoul? "No. His systems, the programs to heal him or me or the big cat, he must have designed and built them before he left home. He can't get home. I stopped that. And if he could, why not just stay?"

  And he thought further: *He's got a program to repair humans and a program for a Kzin. For a Ghoul he'd have to write a new program. What my life would cost me is already too much, but what would it cost to write a treatment program for yet another species? And if Louis Wu asked him to save a Ghoul, then why not a Weaver next? A City Builder? A ...?*

  *Impossible.*

  The hidden Ghoul had accepted that ... or else he was thinking that some wanderers were mad. Kazarp was playing again. Louis said, "When I thought I'd murdered so many people ... I decided to age and die in traditional fashion. How bad could it be? People have done that since there were people."

  "Luweewu, I would give all I have to be a hundred falans younger."

  "The Web Dweller can do that for me ... for my species. He can do it again when I get old again. Demanding anything he likes of me, each time."