The Ringworld Engineers

springy under his weight as he climbed. He passed doors marked in gold, all closed. Higher up, arched openings led to banks of reading screens with chairs. Louis counted forty-six City Builders using reading screens, and two elderly Machine People, and a compact, very hairy male you-name-it, and a ghoul woman all alone in one room.

The top floor was the map room. He knew when he had reached it.

They had found the first map room in an abandoned floating palace. Its wall was a ring of blue mottled with white. There had been globes of ten oxygen-atmosphere worlds, and a screen that would show a magnified view. But the scenes it showed were thousands of years old. They showed a bustling Ringworld civilization: glowing cities; craft zipping through rectangular loops along the rim wall; aircraft as big as this library: spacecraft much bigger.

They had not been looking for a Repair Center then. They’d been looking for a way off the Ringworld. Clearly the old tapes had been almost useless.

They’d been in too much of a hurry. So: twenty-three years later, in another kind of desperation, we try again…

Louis Wu emerged from the stairwell with the Ringworld glowing around him. Where the sun would have been, there was Louis Wu’s head. The map was two feet tall and almost four hundred feet in diameter. The shadow squares were the same height, but much closer in, hovering over a thousand square feet of jet black floor flecked with thousands of stars. The ceiling, too, was black spattered with stars.

Louis walked toward one of the shadow squares, and through it. Holograms, right, as with that earlier map room. But this time there were no globes of Earthlike worlds.

He turned to inspect the back of a shadow square. No detail showed: nothing but a dead-black rectangle, slightly curved.

The magnification screen was in use.

A three-foot-by-two-foot rectangular screen, with controls below, was mounted on a circular track that ran between the shadow squares and the Ringworld. The boy had an expanded view of one of the mounted Bussard ramjets. It showed as a glare of bluish light. The boy was trying to squint past it.

He must have just reached adolescence. Very fine brown hair covered his entire scalp, thickening at the back. He wore a librarian’s blue robes. His collar was wide and square, almost a cape, with a single notch cut into it.

Louis asked, “May I look over your shoulder?”

The boy turned. His features were small and nearly unreadable, as with any City Builder. It made him look older. “Are you allowed such knowledge?”

“Lyar Building has purchased full privileges for me.”

“Oh.” The boy turned back. “We can’t see anything anyway. In two days they’ll turn off the flames.”

“What are you watching?”

“The repair crew.”

Louis squinted into the glare. A storm of blue-white light filled the screen, with darkness at its core. The attitude jet was a dim pinkish dot at the center of the darkness.

Electromagnetic lines of force gathered the hot hydrogen of the solar wind, guided and compressed it to fusion temperatures, and fired it back at the sun. Machinery strove with single-minded futility to hold the Ringworld against the gravity of its star. But this was all that showed: blue-white light and a pinkish dot on the line of the rim wall.

“They’re almost finished,” the boy said. “We thought they’d call us for help, but they never came.” He sounded wistful.

“Maybe you don’t have the tools to hear them calling.” Louis tried to keep his voice calm. Repair crew! “They must be finished anyway. There aren’t any more motors.”

“No. Look.” The boy set the view zipping along the rim wall. The view stopped, jarringly, well beyond the blue glare. Louis saw bits of metal falling along the rim wall.

He studied them until he was certain. Bars of metal, a great spool-shaped cylinder — those were the dismantled components of what he had seen through Needle’s telescope. That was the scaffolding for remounting the Ringworld’s attitude jets.

The repair crew must have decelerated this equipment to solar orbital speed by using a segment of the rim transport system. But how did they plan to reverse the procedure? The machinery would have to be accelerated to Ringworld rotational speed at its destination.

By friction with the atmosphere? Those materials could be as durable as scrith. If so, heating would not be a problem.

“And here.” The view skidded again, spinward along the rim wall to the spaceport ledge. The four great City Builder ships showed clear. Hot Needle of Inquiry was a speck. Louis would have missed it if he hadn’t known just where to look: a mile from the only ship that still sported a Bussard ramjet around its waist.

“There, you see?” The boy pointed to the pair of copper-colored toroids. “There’s only one motor left. When the repair crew mounts that, they’ll be finished.”

Megatons of construction equipment were falling down the rim wall, no doubt accompanied by hordes of construction men of unknown species, all aimed at Needle’s parking space. The Hindmost would not be pleased.

“Finished, yes,” Louis said. “It won’t be enough.”

“Enough for what?”

“Never mind. How long have they been working, this repair team? Where did they come from?”

“Nobody wants to tell me anything,” the boy said. “Flup. Odorous flup. What’s everybody so excited about? Why am I asking you? You don’t know either.”

Louis let that pass. “Who are they? How did they find out about the danger?”

“Nobody knows. We didn’t know anything about them till they started putting up the machines.”

“How long ago?”

“Eight falans.”

Fast work, Louis thought. Just over a year and a half, plus whatever time it took them to get ready. Who were they? Intelligent, quick, decisive, not overwhelmed by large projects and large numbers — they might almost be… but the protectors were long gone. They had to be.

“Have they done other repairs?”

“Teacher Wilp thinks they’ve been unblocking the spillpipes. We’ve seen fog around some of the spill mountains. Wouldn’t that be a big thing, unblocking a spillpipe?”

Louis thought about it. “Big, all right. If you could get the sea-bottom dredges going again… you’d still have to heat the pipes. They run under the world. The sea-bottom ooze in a blocked pipe would freeze, I think.”

“Flup,” said the boy.

“What?”

“The brown stuff that comes out of a spillpipe is called flup.”

“Oh.”

“Where are you from?”

Louis grinned. “I came from the stars, in this.” He reached past the boy’s shoulder to point out the speck that was Hot Needle of Inquiry. The boy’s eyes grew big.

More clumsily than the boy had, Louis ran the view along the path the lander had taken since leaving the rim wall. He found a continent-sized expanse of white cloud where the sunflower patch had been. Farther to port was a wide green swamp, then a river that had cut itself a new bed, leaving the old as a twisting brown track through the yellow-brown desert. He followed the dry riverbed. He showed the boy the city of vampires; the boy nodded.

The boy wanted to believe. Men from the stars, come to help us! Yet he was afraid to look gullible. Louis grinned at him and continued.

The land turned green again. The Machine People road was easy to follow; in most places the land was clearly different to either side. Here the river curved back to join its old bed. He ran the scale up again and was