Nessus had been steering when they left Zignamuclickclick. Later he had turned the fleet over to Speaker. They had flown all night. Now, overhead, a brighter glow along one edge of the central shadow square showed that dawn was near.

Sometime during these past hours, Louis had found a way to visualize the scale of the Ringworld.

It involved a Mercator projection of the planet Earth — a common, rectangular, classroom wall map — but with the equator drawn to one-to-one scale. One could relief-sculpt such a map, so that standing near the equator would be exactly like standing on the real Earth. But one could draw forty such maps, edge to edge, across the width of the Ringworld.

Such a map would be greater in area than the Earth. But one could map it into the Ringworld's topography, and look away for a moment, and never be able to find it again.

One could play cuter tricks than that, given the tools that shaped the Ringworld. Those matching salt oceans, one on each side on the ring, had each been larger in area than any world in human space. Continents, after all, were only large islands. One could map the Earth onto such an ocean and still have room left over at the borders.

I shouldn't have laughed, Louis told himself. It took me long enough to grasp the scale of this … artifact. Why should I expect the natives to be more sophisticated?

Nessus had seen it earlier. Night before last, when they had first seen the arch, Nessus had screamed and tried to hide.

"Oh, what the tanj …" It didn't matter. Not when all mistakes could be left behind at twelve hundred miles per hour.

Presently Speaker called and turned control of the fleet over to Lotus. Louis flew while Speaker slept.

And dawn came on at seven hundred miles per second.

The line dividing day from night is called the terminator. On Earth the terminator is visible from the Moon; it is visible from orbit; but it cannot be seen from the Earth's surface.

But the straight lines dividing light from dark on the arch of the Ringworld were all terminators.

From spinward, the terminator line swept toward the flycycle fleet From ground to sky it ran, from infinity-port to infinity-starboard. It came on like destiny made visible, a moving wall too big to go around.

It arrived. The corona brightened overhead, then blazed as the withdrawing shadow square exposed a rim of solar disc. Louis contemplated the night to his left, the day on his right, the terminator shadow receding across an endless plain. A strange dawn, staged for Lotus Wu the tourist.

Far to starboard, beyond where the land turned to haze, the sharp outlines of a mountain peak materialized in the new daylight.

"Fist-of-God," said Louis Wu, tasting the rolling sound of it in his mouth. What a name for a mountain! But especially, what a name for the greatest mountain in the world!

Louis Wit the man ached. If his body didn't begin adjusting soon, his jouints would freeze him in sitting position and he'd never move again. Furthermore, his food bricks were beginning to taste like — bricks. Moreover, his nose was still partly numb. And there still wasn't any coffee spigot.

But Louis Wu the tourist was being royally entertained. Take the puppeteer flight reflex. Nobody had ever suspected that it might also be a fighting reflex. Nobody but Louis Wu.

Take the starseed lure. What a poetic thing to leave lying about! A simple device, invented thousands of years ago, Nessus had said. And no puppeteer had ever thought to mention it, until yesterday.

But puppeteers wen so completely unpoetic.

Did the puppeteers know why Outsider ships followed starseeds? Did they gloat in the knowledge? Or had they learned that secret, then discarded it as irrelevant to the business of living forever?

Nessus was out of the intercom circuit. Asleep, probably. Louis signaled him, so that the puppeteer would see the light on his panel and call him when he woke.

Did he know?

The starseeds: mindless beings who swarmed in the galactic core. Their metabolism was the solar phoenix, their food was the thinly-spread hydrogen of interstellar space. Their motive power was a photon sail, enormous and highly reflective, controlled like a skydiver's parachute. A starseed's egg-laying flight commonly took it from the galactic axis out to the edge of intergalactic space and then back, without the egg. The hatched starseed chick must find its own way home, riding the photon wind, to the warm, hydrogen-rich core.

Where the starseeds went, then went the Outsiders.

Why did Outsiders follow starseeds? Whimsical question, though poetic.

Maybe not so whimsical. Back around the middle of the first Man-Kzin war a starseed had zigged instead of zagging. The Outsider ship following it had cruised past Procyon. Had paused long enough to sell We Made It a hyperdrive shunt.

The ship could as easily have wandered into kzinti instead of human space.

Amd hadn't the Puppeteers been studying the kzinti about that time?

"Tanjit! That's what I get for letting my mind wander. Discipline, that's what I need."

But hadn't they? Sure they had. Nessus had said so. The puppeteers had been researching the kzinti, investigating whether they could be exterminated safely.

Then the Man-Kzin war had solved their problem. An Outsider ship had wandered into human space to sell We Made It a hyperdrive shunt, while the kzinti armada was sweeping inward from the opposite border. Once human warships had the hyperdrive shunt, the kzinti had ceased to be a threat to man and puppeteer alike.

"They wouldn't dare," Louis told himself. He was appalled.

"If Speaker ever -" But that possibility was even worse.

"An experiment in selective breeding," said Louis. "Selective there-ain't-no-justice breeding. But they used us. They used us!"

"Yes," said Speaker-To-Animals.

For an instant Louis was sure he had imagined it. Then he saw Speaker's transparent, miniature image at the top of his dashboard. He had left the intercom open.

"Tanj for torment! You were listening!"

"Not by choice, Louis. I neglected to switch off my intercom."

"Oh." Too late, Louis remembered Speaker grinning at him, supposedly out of hearing range, after Nessus had finished describing a starseed lure. Remembered that kzinti ears were made to serve a hunting carnivore. Remembered that the kzinti smile reflex is intended to free the teeth for battle.

"You mentioned selective breeding," said Speaker.

"I was just -" Louis floundered.

"The puppeteers pitted our species against each other in order to restrict kzinti expansion. They had a starseed lure, Louis. They used it to guide an Outsider ship into your space, to ensure a human victory. An experiment in selective breeding, you called it."

"Listen, times a very chancy chain of assumptions. If you'll just calm down -"

"But we both followed that chain."

"Um."

"I was in doubt as to whether to broach the subject to Nessus, or whether to wait until we had accomplished our major objective, which is to leave the Ringworld. Now that you know the situation, I have no choice."

"But -" Louis closed his mouth. The siren would have drowned him out anyway. Speaker had signaled emergency.

The siren was a maniac mechanical scream, a subsonic and supersonic and jarringly painful sound. Nessus appeared above the dash, crying, "Yes? Yes?"

Speaker roared his answer. "You have meddled in a war in the enemy's favor! Your action is tantamount to a declaration of war against the Patriarchy!"

Teela had cut in in time to hear the last part. Louis caught her eye, shook his head. Dont mix in.