"Didn't you have a contract?"

  "Not then."

  "I learned how to use stepping disks. Come here."

  The knobby man had lockpicking tools made of hardwood. He knelt by the disk and lifted its edge.

  Louis couldn't see what he was doing. The protector's fingers worked too fast. He saw the stepping disk diagram appear in the Hindmost's quarters, and flicker. Then the protector set the disk in place, pushed Louis onto the stepping disk and followed.

  ***

  With the lander destroyed, the lander bay was mostly empty space. There were suits for men and kzinti and puppeteers. The transparent walls of the airlock opened into a tunnel that led through several cubic miles of magma, undisturbed since the war with Teela Brown.

  Louis glanced at the weapons racks but did not approach them. He pulled out a skintight pressure suit already zipped open along the torso, sleeves, and legs. He wouldn't need the cummerbund. He started to crawl into it, and stopped with a gasp of pain.

  Before he could ask for help, the protector was there, easing his half-healed hand and arm into the sleeve and glove, then fashioning a sling from the tie that had been Acolyte's tourniquet. He zipped up Louis's suit, screwed a helmet onto the neck ring, and set an air rack on his back. They waited for the suit to contract to Louis's own shape.

  The knobby man worked the controls of the big stepping disk the cargo disk. Louis began his checklist. *Helmet camera, airflow, air recycler, CO2 and water vapor content --*

  The knobby man pulled him through.

  Chapter 20 -

  Bram's Tale

  REPAIR CENTER METEOR DEFENSE, A.D. 2892

  The Map of Mars stood forty miles high above the GreatOcean, a north polar projection at one-to-one scale. From the Ringworld's underside there was no sign of the Map of Mars, because the entire forty-mile-high pillbox was hollow.

  Louis had seen vast spaces inside the RepairCenter, but he had never been inside this one. It was huge and dark. Skeletal chairs equipped with lap keyboards rode on long booms. The ellipsoidal wall was a display screen thirty feet high. The only light came from the screen: a wraparound view of the local sky.

  There were no planets or asteroids in Ringworld system. The Ringworld engineers must have cleared all of that out, or used it as building material. The Ringworld's night-shadowed rim showed pale against the black background. Light-amplified stars glared, and four tiny green circles: cursors.

  "I found four more," the Hindmost said. He was at a wall of clumsy, clunky lights and dials and switches. Now Louis recognized where he was. This was the system that twisted the sun's magnetic field. He had seen this array in a holo projection, eleven years ago, when the Hindmost manipulated the Meteor Defense.

  The air here must be soupy with tree-of-life spores.

  It was a tidy place, except -- hmmm?

  Across that great width of floor, a shadow-shape was standing in near darkness. A shape of motionless menace, skewed from the human shape, too thin and too pointy in spots. Bones. Bones mounted in a pose of attack.

  In the shadows beyond those standing bones, gear seemed scattered at random.

  *Later.* Louis said, "I should finish my checklist. Do you need me instantly?"

  The knobby man said, "No. Hindmost, show me."

  No Belter would have yanked a man into a vacuum before he had checked his pressure suit. That would be murderously rude. Had the protector read the readiness of his suit at a glance? Louis wondered. Was the protector testing his attitude? His equipment? His temper?

  The Hindmost was riding one of the cargo plates. He lifted by a yard; his heads dipped among the controls. The skyview zoomed on an orange near-sphere marked in black dots-and-commas. A kzinti ship, probably centuries old and retrofitted with hyperdrive.

  The view shrank, and moved, and expanded. This next ship looked big, a long, slowly rotating lever with a bubble at the near end. Louis didn't recognize the type.

  The view shrank and moved and expanded to show a gray and black object like a diseased potato seen through fog. The Hindmost said, "The Ringworld engineers left only the most distant comets. Too many to destroy them all --"

  "Air reserve," the knobby man said. "To replace air lost over the rim walls."

  "... Yes. Now note this ..." A blinking green circle marked a crater on the proto-comet. The view expanded, then shifted to deep-radar, with a blurred view of structure in the ice below the pock.

  The knobby man asked, "What species built that?"

  "I can't tell," the Hindmost said. "Mining projects always have that look, like the root system of a plant. But here ..." Another rotating lever, a ship of the same make, viewed from the side. Familiar little stubby-winged aerospacecraft were strung all along its length.

  "These are United Nations craft made by Louis's species."

  Louis had finished his checklist. The suit would keep him alive for weeks, maybe months.

  "Very good. Allow me," the knobby man said. He stepped on another cargo plate, and rose. His hands were dexterous where the puppeteer's mouths had been unsure. A second screen lit with a darkened view of the sun.

  Minutes passed. Then a bright plume began to rise, twisting in magnetic fields.

  Louis said, "You're going to kill them, I take it."

  "Such are my directions. They came as invaders," the Hindmost said.

  "So did we."

  "Yes. Are you healthy?"

  Louis wiggled his bound hand. "Healing. It's a waste of time, anyway, if I'm going into your magic 'doc. What have you been doing?"

  "We've destroyed six carrier ships and a fleet of thirty-two landers. Those were the ships closest to the sun, the most vulnerable. These last are so distant that we may do no more than enrage them. I'm inclined to ignore the installation in the comet. We would only boil ice. I found an Outsider ship on one of the farthest comets --"

  "Tanj! Knobby man? You didn't shoot down an Outsider, did you?"

  "The Hindmost advised against."

  "Good. They're very fragile, but they've got technology we can't even properly *describe*. For that matter, they don't want anything we've got, and what they want, they buy. There'd be no point to hurting an Outsider."

  "Do you like them?"

  That was a somewhat surprising question. Louis said, "Yes."

  "What would they be doing here?"

  Louis shrugged inside his suit. "The sky is full of planets. There's only one Ringworld. Outsiders are curious."

  The solar plume was still rising. "Observe and criticize," the knobby man said to the Hindmost. Fingers like strings of walnuts danced over the wall.

  The puppeteer watched. He said, "Good."

  It all seemed very leisurely. The plume would take hours to form. The superthermal laser effect would be propagating for minutes before it left the plume. The targets looked to be hours away at lightspeed.

  Louis had already discarded the notion of a last minute rescue.

  Louis Wu owed nothing at all to the United Nations or the ARM. He wasn't obliged to protect kzinti ships either. Disarmed and injured, he was no match for a protector of any species. He knew he'd be lucky to keep his life, now that he was back in this dance of powers.

  His contract didn't bind him to rescue the knobby man's prey. And they *had* come as invaders.

  "I pointed out a monitor station, too. One of mine," the Hindmost was saying. "The Conservatives will never miss it."

  "Right. Knobby man, I'm tempted to call you 'Dracula.' Dracula was the archetype of story vampires."

  "Follow your whim."

  "No. Trite. You're a protector, a prime mover among vampires. Let's call you 'Bram.' Can you tell me what you want of
me?"

  "I want what is best for my species. Vampires face three threats, and each threatens all beneath the Arch including yourselves."

  The knobby man watched Louis's face as he spoke. "First, if vampires become numerous, we deplete our prey. Intelligent hominids might even find a way to exterminate us. *I* don't want any species of vampire getting too much attention. *You* don't want us spreading."

  "The vampire slayers, were they yours? No, that's crazy. They're your own species."

  "No, Louis, they're not. There must be a hundred separate species of vampire on the Ringworld."

  "Ah. Where do yours live?"

  Bram ignored that. "Louis, I did not shape the Shadow Nest Alliance. Their solution was elegant, wasn't it?"

  "Yeah."

  "Second, these invaders from space threaten the Ringworld structure itself."

  Louis nodded. "An interstellar warship can always use a meteoroid impact for a weapon. Watch for falling comets."

  "The third threat is protectors, for the duels they fight."

  Louis asked, "Just how many protectors have we got already?"

  "Three or more involved in repairing the rim wall installations. Each would seem to have its task, but all will bear watching."

  "What species, can you tell?"

  "It's an important question, isn't it? Those who rule would be vampires. Any others would be servants drafted from local species. Louis, one can argue --"

  "How the tanj did the Ringworld come to be infested with vampire protectors?"

  "That is an intricate tale, but why should I tell it?"

  Louis had carefully *not* bound himself or the Hindmost to reveal secrets. How could he urge Bram to reveal his? He said, "It's your call. First decide what you want. Decide if we can give it to you. Then decide how much we need to know to do it right."

  The knobby man's hand danced over the wall. He said, "You keep secrets. Why should I tell mine? You are bound to obey regardless."

  *Try this --* "You've been shooting down ships. Stet, but suppose you miss one? You've no way to judge what they'll do next. We three, I and Acolyte and the Hindmost, are the only aliens at hand. You expect to watch us and extrapolate what invaders would do. But we don't react if we don't know anything."

  The bright plume pulled from the sun had been arcing over, but now it started to straighten, to narrow. Bram said, "Hindmost?"

  "The prominence is nearly in place."

  "Will you complete the maneuver?"

  "Destroy all four sources?"

  "Leave the comet. Louis, how can you react properly if you know you're being watched?"

  "When I'm being watched, I watch back. Take it into account. Bram, who *are* you? How did a vampire get into the RepairCenter?"

  "I mapped my way in."

  Louis waited.

  "Louis, have you seen how hominids behave when they drink the fuel the Machine People make?"

  "I've done it myself."

  "I never have. Now you must imagine that you have drunk fuel beginning with your mother's milk. Tens of falans later you wake sober for the first time, sober and buzzing with energy and ambition.

  "I was born ... I was *shaped* 7,200 falans ago. Corpses lay all about me, tens of my kind, days dead, and one strange shape that was all knobs. I was all knobs, too, sexless, and cold and hungry and gashed by fighting, but I was solving the world like a great puzzle. Three others were waking, changed like me."

  Louis asked, "You *trapped a protector*? Vampires aren't that intelligent."

  "This one was born trapped, made to be a servant."

  Made by ...? "Go on."

  "The city stood on a vertical cliff and one great stilt. I was born in its shadow. We were always hungry. A ramp wound up the stilt to the smell of prey, but iron lace stung us when we tried to climb the ramp or the mountain face. Transport flew to and fro. The ramp was never used. After we became protectors, we guessed at the reasons our lives ran as they did. I think we were a defense --"

  "Moat monsters," Louis said. "Invaders would have to face vampires before they reach the real guards."

  "Plausible," the knobby man said. "There came a famine, when no more produce flowed into the city. A lost war, political games, bandits on the roads, who can tell? We vampires knew only that the flow of garbage slowed to a trickle, and water and sewage, too. What ate of the garbage went elsewhere, and we who survived partly on scavengers' blood began to starve.

  "Many days later the iron lace barrier lifted and great boxes rolled down the ramp. We tried to get them open, get to the blood within. Their wheels rolled over us. A fantastic warrior danced about the vehicles and killed all who came, and stayed after the vehicles were gone, killing all who would follow. She would not heed our pleading --"

  "Pleading?"

  "She was immune to our scent and ignored our body language. That enraged us. We had never seen a protector. We were stupid and angry and hungry. We brought the knobby one down at last, swarmed her and took what blood she hadn't lost in the fight, and were still hungry enough to drink from our fallen. Then others fell into a sleep like death, and so did I.

  "When I woke, I was changed. But I remembered, and that was already a new thing.

  "Many of us tasted protector blood that day. Some died in their sleep. Four protectors woke. By her scent, one was my favored mate, and so we knew each other."

  "I wondered. Vampires are monogamous?"

  "Say?"

  "Mate once."

  "No, Louis. When a hominid doesn't have the scent, that is prey. I drink her veins empty while I rish. Her scent may mark a woman as my kind and make her safe. But we were *starving*, Louis. She and I, my mate, what shall I call her ...?"

  It surprised Louis, the fervor with which Bram told a tale he'd had to be goaded into. Was this the first time he'd ever had listeners? He said, "Anne?"

  "Anne and I had the will to keep our mouths shut while we mated. Of course we never mated after we woke changed, but we remembered that we trusted each other."

  The memory took him by surprise, and Louis shuddered. *Trust a vampire?*

  She had seemed an angel in rut, supernaturally desirable, the vampire who attacked Louis Wu twelve years ago. His hands in her ash-blond curls had found too much hair, too little skull capacity. It was not possible for another hominid to judge what a Ringworld vampire really was.

  Louis could see the Hindmost listening: one head cocked toward Bram and him, while the other worked at the board. He said, "Stet, go on."

  "We four explored, with ten breeders too young to make the change. My mind made maps as we went. WedgeCity was a triangle, the base supported by a mountain face, the point resting on the great stilt, the stilt rising farther to form a tower. We battered down doors and smashed windows, but the only hominids in the city were imprisoned in the tower. When our breeders had been fed and the edge was off our hunger, we followed a scent trail to a better protected place, a place where two protectors had lived above a hidden store of yellow roots. You know of these roots?"

  "Tree-of-life."

  "We saw their nature. Anne and I, we saw that the root was our blood now. We would starve without it. We killed the others."

  "That first protector --"

  "I studied her body," Bram said. "She was smaller than me. Her jaw was massive, specialized to chew tough branches that grew locally. Her tools were primitive. She rescued breeders of her own local species, fought to cover their passage out of the city and through the vampires, and sacrificed her life in the act.

  "Louis, most life, most animals, most *hominids*, can only survive in one locale. Imagine that your species is restricted to some one stretch of river, clump of forest, isolated
valley or swamp or desert. As a protector, you become more flexible, but everything you cherish is in one place. A protector of a less restricted kind can destroy it all if you don't obey her commands."

  "Did you see any sign of --"

  "Yes, of course, clues were everywhere, they crawled up on our shoulders to bite our necks! Two protectors dwelt in the house of the roots. One served the other. We found bodies, breeders of the servant's species. The master was of another kind, near eighty thousand falans old, protector of a species that has since changed or become extinct. I knew the smell of him thousands of falans later. The famine drove him from WedgeCity. The servant stayed to rescue her species."

  "Her *blood* made you a protector."

  "Evidently," Bram agreed.

  "The virus. The gene-changing virus in tree-of-life root. It's in the blood of protectors, too." Louis found that amusing. *Vampires become immortal by drinking an immortal's blood!*

  But it did not amuse him to be at the mercy of a vampire protector.

  Now the plume from the sun stretched tens of millions of miles into space. The Hindmost rode a cargo plate near the rounded ceiling, one head cocked to hear. Surely he was too far away. Unless ... a directional mike?

  Louis asked again, "How did you get into the RepairCenter?"

  Bram said, "Roots to last a hundred falans. We must find the source or die when we run out. Anne and I taught each other to read. Writings in WedgeCity guided us to cities with libraries. We chose a cold climate so that we might hide ourselves under clothing. They took us for visitors from afar. We paid taxes, bought land, ultimately gained a citizen's access to the library of the Delta People.

  "There we learned something of the repair facilities beneath the Map of Mars.

  "We reached the GreatOcean and crossed it. We had to make inflated cylinders to walk about the surface of the Map of Mars. I prefer your pressure suits. Still, we entered while still alive."