At first Mur looked back frequently into the Crust-forest. Dia's face, turned down like a small, round leaf, followed them as they descended, her expression soon too distant to read. Then she ducked back into the forest. For a while Mur was able to follow the movements of the other Human Beings as they worked through the forest, using the time to hunt and to repair damaged tools, ropes and clothes. But at last the site of the Human Beings' temporary camp was lost in the swirling, complex tapestry of trunks and branches that made up the Crust-forest.

Mur spent some time staring up at the forest, carefully committing the pattern of trunks to memory so they could find the Human Beings again.

Philas descended toward the artifact without speaking. Her thin face was intent on the goal, empty of expression; Mur hadn't seen her so focused since the death of Esk. She dug into her pouch and, with efficient regularity, bit into a piece of meat.

Mur , alone with his thoughts, fell through the vortex lines. The artifact, and the little colony around it, grew in his vision tantalizingly slowly. But it wasn't long before he could see without ambiguity that the artifact was indeed a tetrahedron, around ten mansheights to a side.

The story of the Colonists, and their Core Wars, was part of the lore of the Human Beings. When the Ur-humans first reached the Star, having traveled from their own unimaginable worlds, the Star was empty of human life. The Colonists had been the first generation to be established within the Star, by the Ur-humans. It had been their task to sp.a.w.n the first of the Star's true inhabitants: all of them, the mortal, frail ancestors of the Human Beings, the people of Parz and the hinterland, all the inhabitants of the Mantle.

Compared to Human Beings the Colonists had been like G.o.ds. They had more in common with the Ur-humans, perhaps, Mur speculated. With Ur-human technology they had pierced the Mantle with wormhole links and established huge Cities which had sailed through the Mantle in vast, orderly arrays. The first generations of Human Beings had worked with their progenitors, traveling the wormhole links and building a Mantle-wide society.

Then the Core Wars had come.

As they neared the artifact, and the irregular little settlement around it, excitement gathered in Mur. Fatigue and hunger worked on him as he Waved, and he became aware that his thinking was becoming looser, more fragmented. His head seemed filled with visions, with new hopes; and the aches of his tired, protesting body seemed to fade. Could these really be Colonists, this artifact a fragment from the magical past?

He wanted to believe. He was tired - so tired - of pain, of death, of sc.r.a.ping his marginal existence from the unforgiving Air. To discover a Colonist artifact would be like returning to the arms of long-dead parents.

Glancing across at Philas, he recognized the same hunger to believe - to find a home - in her expression, the set of her body as she Waved.

With perhaps five hundred mansheights separating them from the artifact, two people broke from the grouping around the tetrahedron. The two came Waving cautiously up to meet Philas and Mur.

Mur slowed, and moved closer to Philas.

The pair from the tetrahedron halted a dozen mansheights below the Human Beings. They were a man and a woman, and they carried spears of wood. The woman came up a little further, and pointed her spear at Mur's belly. "What do you want?"

Mur inspected the woman. She must have been aged around forty. The spear was well crafted, but it was just a spear - nothing more sophisticated than a sharpened stick of wood, nothing the Human Beings couldn't have manufactured for themselves. The woman wore a crude, pocketed poncho of what looked like pig-leather, and a wide-brimmed hat. Folds of cloth were tied up around the rim of the hat. The woman was well muscled but scrawny; her face was wide and flat, disfigured by a scowl. "Well?" she demanded. "Deaf, are you?"

Mur sighed, disappointment gathering in him. He turned to Philas. "Obviously, these aren't Colonists."

"Who are they, then?"

"How should I know?" he snapped back, irritated.

He moved forward a little, with arms spread wide, hands empty. "My name is Mur. This is Philas. We're - refugees." He decided not to mention the rest of the Human Beings. "We lost all we possessed in the Glitch. We're trying to get to Parz City. Do you know it?"

The woman's eyes narrowed; she didn't reply. She raised the spear uncertainly and poked it toward Mur's stomach again, subst.i.tuting aggressiveness for an answer.

"We're wasting our time," Mur whispered to Philas. But Philas had broken away from him and was Waving down with irregular, trembling strokes of her thin legs toward the strangers.

"You have an Interface," she said.

The man, similarly grimy and scowling, a little younger than the woman, joined his companion. He too was wearing a battered, wide-brimmed hat. They stared at the Human Beings as suspiciously, thought Mur, as a pair of tethered Air-pigs.

"Please," Philas said. "We've come a long way. We're trying to reach the Pole. Can we..." She stumbled over her words, as if she'd become suddenly aware of how foolish they sounded. "Will your Interface help us?" She looked from one to the other. "Do you understand what I'm asking?"

The man opened a mouth devoid of teeth and laughed, but the woman laid a restraining hand on his arm. Her voice remained stern, but it softened a little. "Yes, I understand. And you're right; it is an Interface - from the olden days, from before the Core Wars. But you can't use it."

Philas was trembling. "We'll pay," she said wildly. "You must..."

Mur grabbed her shoulders and tried to still her shivering with his own inertia. "Stop it, Philas. Don't you understand? Even if we could pay, the Interface doesn't work any more. the Interface doesn't work any more. These people are as helpless as we are." These people are as helpless as we are."

Philas stared into his face resentfully, then turned away; her body was wracked by shuddering.

The man and woman watched them curiously.

Mur turned to them wearily. "Why don't you put away your weapons? You can see we're no threat to you."

They lowered their spears carefully, but kept them aimed roughly in the direction of the Human Beings. The man said, "You really are refugees from further upflux?"

"Yes. And we really are trying to reach a place called Parz City, which we've never seen. But it's at the Pole."

"Which Pole?" the woman asked. "The South Pole?"

The man cackled. "If you're starting from here it hardly matters, does it?"

"Oh, shut up, Borz," the woman said.

Mur put his arm around Philas. "Will you let us see your Interface?"

To his shame, he read amused pity in the woman's expression. "If you want," she said. "But stay close to the two of us. Do you understand? We see enough thieves and beggars..."

"We're no beggars," Philas said with a spark of spirit. She drew away from Mur and pulled her shoulders straight.

"Come, then."

Borz and the woman turned away from them and separated by a couple of mansheights. Hand in hand, Mur and Philas Waved cautiously forward.

Soon they were approaching the artifact, shepherded by spears and scowls.

Mur squeezed Philas's hand. "You should have said we weren't thieves," he whispered. "I was thinking of trying a little begging."

She managed a small laugh. "It wouldn't have worked. These people have no more than we have... or had, before we lost our home." She pointed at Borz, to their left. "Look at the hat he's wearing."

The hat's brim was piled with pleats of fine material, knotted into place by ties fixed through holes in the leather of the hat. Mur imagined undoing those ties; perhaps a kind of net would drop down, around the head.

"It's odd, but what about it?"

"Remember Dura's tales of her time on the ceiling-farm. The Air-tanks they made her wear, working high up, close to the Crust. The masks..."

"Oh. Right." Mur nodded. "Those hats must have come from coolies' Air-tanks."

"So my guess is these people used to be coolies. Maybe they ran away."

"But they ought to know about Parz."

Philas laughed without humor. She seemed in control of herself again, but her mood was black. "So they are concealing things from us. Well, we lied to them. That's what the world is like, it seems."

Mur stared at Borz's hat. Apart from Deni Maxx's Air-car it was the first artifact even remotely related to the City he'd ever seen. And recognizing it now from Dura's description somehow lent veracity to Dura's bizarre tale. He felt oddly rea.s.sured by the confirmation of this small detail, as if somewhere inwardly he'd imagined Dura might be lying, or mad.

The people turned to stare, suspicious and hostile, as the Human Beings were brought into the encampment by Borz and his companion. There seemed to be around forty humans in the little colony, perhaps fifteen of them children and infants. The adults were fixing clothes, mending nets, sharpening knives, lounging in the Air and talking. Children wriggled around them like tiny rays, their bare skins crackling with electron gas. None of it would have looked out of place in any of the Human Beings' encampments, Mur thought.

The tetrahedral artifact loomed beyond the small-scale human activities. It was a skeletal framework, incongruous, sharp, dark.

Borz and the woman hung back as Mur and Philas hesitantly approached the tetrahedron's forbidding geometries. Mur peered up at the framework. The edges were poles a little thicker than his wrist, each about ten mansheights long. They were precisely machined of some dull, dark substance. The four triangular faces defined by the edges enclosed nothing but ordinary Air - in fact, the people here had slung sections of net to enclose a small herd of squabbling, starved-looking Air-pigs at the framework's geometric center. Elsewhere on the framework rough bags had been fixed by bits of rope; irregular bulges told Mur that the bags probably contained food, clothes and tools.

Mur moved forward, reached out a tentative hand and laid his palm against one edge. The material was smooth, hard and cold to the touch. Maybe this was the Corestuff of which Dura had spoken, extracted from the forbidding depths of the underMantle by City folk (and now, unimaginably, by the boy Farr whom Mur had grown up with).

Philas asked, "Can we go inside?"

The woman laughed. "Of course you can. Your friend was right... nothing works, any more."

The man grunted to Mur. "We'd hardly keep our pigs in there if they were going to be whisked off to the North Pole at any moment."

"I imagine not."

Philas pa.s.sed cautiously through one face of the tetrahedron. Mur saw her shiver as she crossed the invisible plane marked by the edges. She hovered close to the pigs and turned in the Air, peering into the corners of the tetrahedron.

The man - Borz - grunted. "Oh, what the h.e.l.l." He dug into one of the bags dangling on the tetrahedral frame and extracted a handful of food. "Here."

Mur grabbed the food. It was stale, slightly stinking Air-pig flesh. Mur allowed himself one deep bite before stuffing the rest into his belt. "Thank you," he said around the mouthful of food. "I can see you've little to spare."

The woman drifted closer to him. "Once," she said slowly, "this frame sparkled blue-white. As if it was made of vortex lines. Can you imagine it? And it really was a wormhole Interface; you could pa.s.s through it and cross the Mantle in a heartbeat." For a moment she sounded sad - nostalgic for days she'd never seen - but now her dismissive expression returned. "So they say, anyway. But then the Core Wars came..."

After raising several generations of Human Beings, the Colonists had suddenly withdrawn. According to the Human Beings' fragmented oral histories the Colonists had retreated into the Core, taking most of the marvelous Ur-human technology with them, and destroying anything they were forced to leave behind.

The Human Beings had been left stranded in the Air, helpless, with no tools save their bare hands.

Perhaps the Colonists had expected the Human Beings to die off, Mur wondered. But they hadn't. Indeed, if Dura's tales of Parz and its hinterland were accurate, they had begun to construct a new society of their own, using nothing but their own ingenuity and the resources of the Star. A civilization which - if not yet Mantle-wide - was at least on a scale to bear comparison with the great days of the ancients.

"The wormholes collapsed," the woman said. "Most of the Interfaces were taken away into the Core. But some of them were left behind, like this one. But its vortex-light died. Now it just drifts around in the Magfield..."

"I wonder what happened to the people inside the wormholes," Mur said. "When the holes collapsed."

Philas came drifting out of the tetrahedron. "Come on, Mur," she said tiredly.

Mur thanked Borz for the sc.r.a.p of food, and nodded to the woman - whose name, he realized, he'd never learned.

The pair barely reacted, and their scowls seemed to be returning. Their spears had never left their hands, Mur noticed.

They Waved out of the little encampment. A child jeered at them, until silenced by a parent; Mur and Philas didn't look back.

They began to Wave upward, side by side.

Mur gazed up at the Crust-forest. "That seems a h.e.l.l of a long way back," he said. "To have come all this way, for a handful of meat..."

"Yes," Philas said savagely, "but we might have found riches. Riches beyond imagining. We had to come."

"I wonder why they stay here, close to the Interface. Do you think it protects them, when Glitches come?"

"I doubt it," Philas said. "After all, the thing floats freely, they said. It's just a relic, a ruin from the past."

"Then why do they stay?"

"For the same reason Dura's City folk built their City at the Pole." Philas waved her hands at the empty Mantlescape, the arching vortex lines. "Because it's a fixed point, in all this emptiness. Something to cling to, to call home." She wiped her eyes with the back of her hand; already she seemed short of breath. "Better than drifting, like we do. Better than that."

Mur lifted his face to the Crust-forest and Waved hard, ignoring the gathering ache in his hips, knees and ankles.

19.

DURA MADE SURE IT WAS SHE, not Farr, whom Hork chose to go on the journey into the underMantle.

At first Adda tried to explain Dura's reasoning to Farr, to provide a bridge between them; but he could see that Farr was devastated. The boy mooched around the Upside apartment Hork had loaned the Human Beings like a trapped Air-pig. Adda wistfully watched him prowl, recalling Logue as a young man. The underMantle journey had many potent elements for Farr - the chance to protect his sibling by taking her place, the intrinsic excitement of the jaunt itself. Farr was still such a melange of boy and man.

But - if one of the three Human Beings must go on this absurd trip - then Dura was the best choice. Farr didn't have the maturity, or Adda himself the strength, to cope with the challenges the journey would provide...

Adda cursed himself silently. Even in the privacy of his own mind he was starting to use the diluted language of the City folk, to be influenced by their gray thinking. Into the Core with that.

The truth was that whoever went down inside this ramshackle craft into the underMantle would almost certainly die there. Dura's qualification was only that she, of the three of them, had the skills and strength marginally to reduce that level of certainty.

So, knowing Dura's decision was right, Adda gave up trying to convince Farr. Instead he tried to support the decision in Farr's mind in subtle ways - by taking the decision as a given, not even trying to justify it. He concentrated on trying to distract Farr from his anxious, angry concern for his sister, which wound up tighter as the day of the Mantlecraft's launch neared. To this end Adda was pleased with the friendships Farr had made in his brief time in the City - with Cris, and the Fisherman Bzya - and tried to encourage them.

When Cris offered to take Farr Surfing again Farr at first refused, unwilling to break out of his absorption with Dura; but Adda pressed him to accept the invitation. In the end it was a little party of four - Cris, Farr, Adda and Bzya - who set off, two days before Dura's launch, through the corridors for the open Air.

Adda had taken a liking to the huge, battered Fisherman, and sensed that Bzya had given Farr a great deal of support - more than Farr realized, probably - during Farr's brief time in the Harbor. Now Farr was free of his indenture, thanks to the whim of Hork V, and - here was the boy showing his immaturity again, Adda reflected - now he seemed to sympathize little with Bzya, who was stuck with the situation Farr had escaped - the huge, stinking halls of the Harbor machines, and the depths of the underMantle. Instead, Farr complained at how little he saw of Bzya.

Adda had no qualms in accepting Bzya's help as they made their way through the busy corridors; the presence of Bzya's huge arm guiding him was somehow less patronizing, less insulting, than any other City man's.

As they traveled out from the core of the City the street-corridors became barer, free of doors and buildings, and the Air more dusty. At last they reached the Skin. It was dark, deserted here, almost disquietingly so, and the City hull stretched above and below them. Adda surveyed the workmanship critically: curving sheets of crudely cut wooden planks, hammered onto a thick framework. It was like being in the interior of a huge mask. From without, the City was imposing, even to a worldly-wise upfluxer like himself; but seen from within, its primitive design and construction were easy to discern. These City folk really weren't so advanced, despite their facility with Corestuff; the Ur-humans would surely have laughed at this wooden box.

They Waved slowly along the Skin, not speaking, until Cris brought them to a small doorway, set into the Skin and locked by a wheel. With Bzya's help Cris turned the stiff wheel - it creaked as it rotated, releasing small puffs of dust - and shoved the door open.

Adda hauled himself through the doorframe and into the open Air. He Waved a few mansheights away from the City and hovered in the Air, breathing in the fresh stuff with a surge of relief. The party had emerged about halfway up the rectangular bulk of the City - in the Midside, Midside, Adda reminded himself - and the skin of Parz, like the face of a giant, cut off half the sky behind him. The imposing curve of a Longitude anchor-band swept over the rough surface a few dozen mansheights off; electron gas fizzed around the band's Corestuff flanks, a visible reminder of the awesome currents flowing through its superconductor structure. Adda reminded himself - and the skin of Parz, like the face of a giant, cut off half the sky behind him. The imposing curve of a Longitude anchor-band swept over the rough surface a few dozen mansheights off; electron gas fizzed around the band's Corestuff flanks, a visible reminder of the awesome currents flowing through its superconductor structure.

Adda's lungs seemed to expand. The vortex lines crossed the shining sky all around him, plunging into the crimson-purple pool that was the Pole beneath the City. The Air here was thick and clammy - they were right over the Pole, after all - but inside the City he always had the feeling he was breathing in someone else's farts.

The two boys tumbled away into the Air, hauling the Surfboard; Adda was pleased to see Farr's natural, youthful vigor coming to the surface as he Waved energetically through the Air, responding to the refreshing openness. Bzya joined Adda; the two older men hung in the Magfield like leaves.

"That door was a little stiff," Adda said drily.

Bzya nodded. "Not many City folk use the pedestrian exits."

Pedestrian. Another antique, meaningless word. Another antique, meaningless word.