The Ringworld Engineers

“The instruments may have recorded something,” the Hindmost said.

“Find out. And take us down to one mile altitude. I think we want to approach the Map of Mars from below the surface.”

“Louis?”

“Do it.”

Chmeee asked, “Have you knowledge of how that laser beam was produced?”

“Louis can tell you,” the puppeteer said. “I will be busy.”

Needle and the lander converged on the Map of Mars from two directions. The Hindmost held the two vehicles parallel so that it was possible to cross between them.

Louis and Chmeee flicked across to the lander for lunch. Chmeee was hungry. He consumed several pounds of red meat, a salmon, a gallon of water. Louis’s own appetite suffered. He was pleased that his guests weren’t watching.

“I don’t understand why you picked up these passengers,” Chmeee said, “unless it was to mate with the woman. But why the boy?”

“They’re City Builders,” Louis said. “Their species ruled most of the Ringworld. And I plucked these two out of a library. Get to know them, Chmeee. Ask them questions.”

“They fear me.”

“You’re a soft-spoken diplomat, remember? I’m going to invite the boy to see the lander. Tell him stories. Tell him about Kzin and hunting parks and the House of the Patriarch’s Past. Tell him how kzinti mate.”

Louis flicked across to Needle, spoke to Kawaresksenjajok, and was back in the lander with him before Harkabeeparolyn quite realized what was happening.

Chmeee showed him how to fly. The lander swooped and did somersaults and darted skyward at his command. The boy was entranced. Chmeee showed him the magic of binocular goggles, and superconductor cloth, and impact armor.

The boy asked about kzinti mating practices.

Chmeee had mated with a female who could talk! It had opened new vistas for him. He told Kawaresksenjajok what he wanted to know — which Louis thought was pretty dull stuff — and then got the boy talking about mating and rishathra.

Kawaresksenjajok had no practice but a lot of theory. “We make records if a species will let us. We have archives of tapes. Some species have things they can do instead of rishathra, or they may like to watch or to talk about it. Some mate in only one position, others only in season, and this carries over. All of this influences trade relationships. There are aids of various kinds. Did Luweewu tell you about vampire perfume?”

They hardly noticed when Louis left to return to Needle alone.

Harkabeeparolyn was upset. “Luweewu, he might hurt Kawa!”

“They’re doing fine,” Louis told her. “Chmeee’s my crewmate, and he likes children of all species. He’s perfectly safe. If you want to be his friend too, scratch him behind the ears.”

“How did you hurt your forehead?”

“I was careless. Look, I know how to calm you down.”

They made love — well, rishathra — on the water bed, with the massage unit going. The woman might have hated Panth Building, but she had learned a good deal. Two hours later, when Louis was sure he would never move again, Harkabeeparolyn stroked his cheek and said, “My time of mating should end tomorrow. Then you may recover.”

“I have mixed feelings about that.” He chuckled.

“Luweewu, I would feel better if you would rejoin Chmeee and Kawa.”

“Okay. Behold as I stagger to my feet. See me at the stepping disc? There I go: poof, gone.”

“Luweewu—”

“Oh, all right.”

The Map of Mars was a dark line, growing, becoming a wall across their path. As Chmeee slowed, microphones on the lander’s hull picked up a steady whispering, louder than the wind of their passage.

They came to a wall of falling water.

From a mile distant it appeared perfectly straight and infinitely long. The top of the waterfall was twenty miles above their heads. The base was hidden in fog. Water thundered in their ears until Chmeee had to turn off the microphones, and then they could hear it through the hull.

“It’s like the water condensers in the city,” the boy said. “This must be where my people learned how to make water condensers. Chmeee, did I tell you about water condensers?”

“Yes. If the City Builders came this far, one wonders if they found the way inside. Do your tales tell anything of a hollow land?”

“No.”

Louis said, “Their magicians are all built like Pak protectors.”

The boy asked, “Luweewu, this great waterfall — why is there so much of it?”

“It must run all the way round the top of the Map. It takes out the water vapor. The top of the Map has to be kept dry,” Louis said. “Hindmost, are you listening?”

“Yes. Your orders?”

“We’ll circle with the lander, using deep-radar and the other instruments. Maybe we’ll find a door under the waterfall. We’ll use Needle to explore the top. How’s our fuel supply?”

“Adequate, given that we won’t be going home.”

“Good. We’ll dismount the probe and set it following Needle at… ten miles and ground-hugging altitude, I think. Keep the stepping-disc links and the microphones open. Chmeee, do you want to fly the lander?”

The kzin said, “Aye, aye.”

“Okay. Come on, Kawa.”

“I’d like to stay here,” the boy said.

“Harkabeeparolyn would kill me. Come on.”

Needle rose twenty miles, and red Mars stretched before them.

Kawaresksenjajok said, “It looks awful.”

Louis ignored that. “At least we know we’re looking for something big. Picture a blowout patch big enough to plug Fist-of-God Mountain. We want a hatch big enough for that patch plus the vehicle to lift it. Where would you put it on the Map of Mars? Hindmost?”

“Under the waterfall,” the Hindmost said. “Who would see? The ocean is empty. The failing water would hide all.”

“Yah. Makes sense. But Chmeee’s searching that. Where else?”

“I must hide the lines of a gigantic hatch in a martian landscape? Perhaps an irregular shape, with hinges in a long, straight canyon. Perhaps I would put it beneath the ice, melting and refreezing the north pole to conceal my comings and goings.”

“Is there a canyon like that?”

“Yes. I did my homework. Louis, the poles are the best gamble. Martians never went near the poles. Water killed them.”

The Map was a polar projection; the south pole was spread out around the rim. “Okay. Take us to the north pole. If we don’t find anything, we’ll spiral out from there. Stay high and keep all instruments going. We don’t care too much if something fires on Needle. Chmeee, are you listening?”

“I hear.”

“Tell us everything. Chances are you’ll find what were after. Don’t try to do anything about it.” Would he obey? “We don’t invade in the lander. We’re burglars. We’d rather be shot at in a General Products hull.”

Deep-radar stopped at the scrith floor. Above the scrith the mountains and valleys showed translucent. There were seas of marsdust fine enough to flow like oil. Under the dust were cities of a sort: stone buildings denser than the dust, with carved walls and rounded corners and a good many openings. The City Builders stared,