To that problem, Speaker had already found the answer.

They were living in pressure suits, before the journey had properly began. Louis sucked pap through a tube, and thought yearningly of steak broiled with a flashlight-laser. Speaker sucked reconstituted blood, and thought his own thoughts.

They certainly didn't need the kitchen. They cut that part of the building loose, and improved the tilt of the building to boot.

They cut away air conditioning and police equipment. The generators that had ruined their flycycles went only after they had been positively identified as separate from the lifting motors. Walls went. Some walls were needed for their shade; for heating became a problem in the direct sunlight.

Day by day they neared the crater at the top of Fist-of-God, a crater that would have swallowed most asteroids. The lip of the crater looked like no impact crater Louis had ever seen. Shards like obsidian spearheads formed a jagged ring. Spearheads the size of mountains themselves. There was a gap between two such peaks … they could enter there …

"I take it," said Speaker, "that you wish to enter the crater itself."

"That's right."

"Then it is good that you noticed the pass. The slope above is too steep for our drive. We should reach the pass very soon."

Speaker was steering the Improbable by modifying the flycycle thrust. That had been necessary since they cut away the stabilizing mechanism in a final attempt to reduce the building's weight. Louis had grown used to the bizarre appearance of the kzin: the five transparent concentric balloons of his pressure suit, the fishbowl helmet with its maze of tongue controls half hiding the kzin's face, the tremendous backpack.

"Calling Prill," Louis said into the intercom. "Calling Halrloprillalar. Are you there, Prill?"

"I am."

"Stay there. We'll be through in twenty minutes."

"Good. You've been long enough at it."

The Arch seemed to blaze above them. A thousand miles above the Ringworld, they could see how the Arch merged into the rim walls and the flat landscape. Like the first man in space, a thousand years ago, looking down on an Earth that, by Jahweh and his mighty hammer, really was round.

"We couldn't have known," said Louis Wu, not loudly. But Speaker looked up from his work.

Louis didn't notice the kzin's odd look. "It would have saved us so much trouble. We could have turned back after we found the shadow square wire. Tanj, we could have dragged the Liar straight up Fist-of-God Mountain behind our flycycles! But then Teela wouldn't have met Seeker."

"The luck of Teela Brown again?"

"Sure." Louis shook himself. "Have I been talking to myself?"

"I have been listening."

"We should have known," said Louis. The gap between the sharp peaks was very near. He felt the urge to babble. "The Engineers would never have built a mountain this high here. They've got over a billion miles of thousand-mile-high mountains, if you count both rim walls."

"But Fist-of-God is real, Louis."

"No, no, no. It's just a shell. Look down; what do you see?"

"Ringworld foundation material."

"We thought it was dirty ice when we first saw it. Dirty ice, in hard vacuum! But forget that aspect. Remember the night you explored a giant map of the Ringworld? You couldn't find Fist-of-God. Why not?"

The kzin didn't answer.

"It wasn't there, that's why not. It wasn't there when the map was made. Prill, are you there?"

"I am here. Why would I leave you?"

"Good. Close the airlock doors. Repeat, close the airlock doors now. Don't cut yourself on the thread."

"My people invented this thread, Louis." Prill's voice was garbled with static. She was off for a minute, then: "Both doors are closed."

The Improbable was passing between the standing shards of mountain. Tense as Louis was, he would have been still more tense; but subconsciously he was expecting a kind of canyon or pass between those peaks.

"Louis, just what do you expect to find in Fist-of-God crater?"

"Stars," said Louis Wa.

The kzin was tense too. "Do not mock me! In all honor -"

— And they were through. There wasn't any pass. There was only a broken eggshell of Ringworld foundation material, stretched by terrific stresses to a few feet of thickness; and beyond that, the crater in Fist-of-God Mountain.

They were falling. And the crater was full of stars.

Louis Wu had an excellent imagination. In his mind's eye the event was perfectly clear.

He saw the, system of the Ringworld, sterile, tidily clean, empty of ramships, empty but for a G2 star and a daisy chain of shadow squares and the Ringworld.

He saw a foreign body passing near, too near. He watched its hyperbolic fall from interstellar space, and he saw its path interrupted — by the underside of the Ringworld.

In his vision the foreign body was about the size of the Earth's Moon.

It must have been ionized plasma in the first seconds. A meteorite can be cooled by ablation, by the boiling away of its own skin. But here the vaporized gas could not expand; it had forced its way into a deforming pocket of the Ringworld floor. The landscape had deformed upward, its carefully planned ecology and rainfall patterns shot to hell over a region greater than the surface of the Earth. All that desert … and Fist-of-God itself, raised a full thousand miles upward before the incredibly tough Ring floor ripped to let the fireball through.

Fist-Of-God? Tanj, yes! Watching from a Ringworld prison cell, Louis Wu had seen it clear in his mind's eye. It must have been visible clear to both rims: a ball of hellfire the size of the Earth's Moon ripping up through the floor of the Ringworld like a strong man's fist through a cardboard box.

The natives could be thankful that the Ring floor had deformed as much as it did. The hole was easily big enough to let all the air out of the Ringworld; but it was a thousand miles too high …

The crater was fall of stars.

And there wasnt any gravity; there wasn't anything for the lifting motors to push against. Louis hadn't really thought this far ahead.

"Grab something," he bellowed, "and hang on! If you fall through the bay window, there'll be no rescue."

"Naturally not," said Speaker. He was wrapped around a naked metal beam. Louis had found another.

"Was I right? Stars!"

"Yes, Louis, but how did you know?"

There was gravity, a steady, heavy pull on the Improbable. The skeleton of a buildiag turned on its side, and the bay window was up.

"It's holding," Louis said fiercely. He wriggled to get right side up on the beam. "It better! I hope Prill strapped down; she'll have a bouncy ride, up the side of Fist-of-God Mountain, riding at the end of ten thousand miles of shadow square wire. Up and over the lip, then -"

They looked up at the underside of the Ringworld. An infinity of sculptured surface. In the middle, a tremendous conical meteor puncture, shiny at the bottom. As the Improbable swung like a plumb bob beneath the Ringworld, the sun flashed suddenly in the bottom of the crater.

"- Out and down. Then we'll be tied to the Liar, and the Liar will be on its way to clear space at 770 miles per second. Plenty of time for the wire to pull us together; but if that doesn't work, we've got the thruster motor in Nessus's flycycle.

"How did I know? I've been telling you that. Didn't I mention the landscape?"

"No."

"That was the clincher. All the peaks of foundation material showing through the rock, and the fall of civilization only fifteen hundred years old! It was because those two asteroid punctures had fouled up the wind patterns. Do you realize that most of the traveling we did was between those two punctures?"