Aaron was explaining something to Raven, who listened intently. "The first barrels just disappeared," he said. "It took a while before we figured out that the coronals expect to find destination and routing labels on incoming and outgoing packages. Then, two months ago we labeled a barrel and dropped it, and forty days later, it came back! Round-tripped! The coronals, they rotate, and the ones in this part of space are lined up, so if you drop something off one at just the right moment, it heads straight for the next one in line, on a tangent to its rim. And the coronals know this ... they're watching for incoming cargos all the time. They'll pick it up ... "

One of the stairwells exploded upward. A bellowing monstrosity stood up into smoke and flame and chunks of rock and metal flew everywhere. The concussion knocked Qiingi off his feet. But they were only two meters below the ceiling now ... one meter, and the workshop was opaqued with smoke. Qiingi let go a long-held breath as the line of light and smoke narrowed and vanished, leaving them alone in a black shaft of rock.

Livia sat disconsolately on a nearby box. Qiingi knelt before her. "Wordweaver Kodaly, are you hurt?" I She shook her head, smiling wanly. "We couldn't save the others." It was half question, half self-accusation.

"Of all of us, who travels best?" he asked. "You should be the one to go on this journey."

Livia tried to brush back her dust-filled hair. "No, I shouldn't. It's precisely because I travel so well that I shouldn't go."

" ... It's a whole system," Aaron was saying to Raven. "Like a subway, only it's shut down. Built to take hundreds, thousands of cars a day between the coronals. Surely it'll be able to recognize and route just one ... "

"I'd been trying not to think about it," Livia said slowly. When Qiingi didn't speak but just continued to look at her, she met his eyes reluctantly. "I mean, how I was able to get us here through all those manifolds. I couldn't understand it myself at first, why some people can travel between manifolds and others can't. Lucius explained it to me, but at the time I refused to understand him. I didn't want to give him the satisfaction of seeing that he was right ... "

"Livia, what are you talking about?"

"So naturally, the system is designed to take objects of all kinds of sizes and shapes," Aaron babbled. "So you're right, you're absolutely right Hell, what does a vessel for traveling in space have to look like, anyway? Does it have to be a vessel, at all ... ?"

As they inched their way up the stone shaft the sounds of battle below reached a crescendo. Then silence, empty except for the low scraping noise of their own ascent.

Livia sighed. "The manifolds have a values-driven interface, right? To visit another manifold, you have to suspend the values of your own. So the person who can travel the best, who can go the farthest is going to be ... the person with no values, no beliefs. The one who believes in nothing." She looked down at Qiingi again, bleakly. "Someone like me."

Qiingi shook his head. "No. It is the exact opposite. The person who travels best is the one who can see the worth of the greatest number of things and people and places."

She shook her head.

"Listen," said Aaron, "you need to adjust your shifts for extreme cold, and gather your angels around you.

We're headed for vacuum in a few minutes." Above them, a square of light was widening slowly.

Qiingi followed Aaron's instructions, but kept an eye on Livia. She seemed listless, spent. The sight alarmed him. After a few minutes the lift ground to a stop on a shelf of rock high above the mountains. The thin wind was bitterly cold, and Qiingi's sinuses and ears hurt As he gasped for breath he felt his totem coil around him protectively, and after a few moments his breath came more easily.

Raven stepped off the platform first; he held out bis hand to help Qiingi. Qiingi hesitated. He couldn't deny that he felt betrayed by this man. But he forced himself to nod curtly and clasp the other's hand as he stepped down onto the cold rock.

They started shifting boxes from the elevator to another open cage that sat outside. This one was rusted and ice-painted, and from its cross-piece roof a thin black cable led up and up, apparently to infinity. The car was mounted to the cliff face by only two frail-looking rails.

When they were done shifting the supplies, they all clambered aboard the new car — all except Raven. He stood perfectly still, a little drift of snow starting around his feet "Go on," he said quietly.

"What are you doing?" asked Livia. "Come on, we need you with us to represent the founders."

The old man shook his head. "You are your manifolds," he said. "And a founder is not a leader. It's better if I stay here and try to aid my people directly. Anyway, somebody has to tell the founders what you're attempting."

"But they'll be waiting for you when you go back down."

Raven smiled wryly. "There's more than one way down."

Qiingi put his hand on Livia's arm. "Come. He has made his decision." Raven nodded to him. Qiingi turned away.

Aaron ordered the new elevator up. They began to rise surprisingly fast. Despite the ache in his heart, Qiingi found his gaze drawn to the vista before him.

Raven stood watching from a narrow ledge on an otherwise vertical plain of rock. A hundred meters below it, glacial ice started and a kilometer farther down the aerie's landing spur was a jumble of blue and green rubble from the avalanche. From there the crags and faces of the mountainside fell away in steps that were veiled in mist and cloud.

Through and between the clouds stretched many fine, threadlike cables, all suspended kilometers above the peaks. The threads dwindled into invisibility where the mountains stretched vast forest-covered fingers onto a distant plain. The land there was just a blue haze filigreed with indistinct detail. It stretched on and on — but not to infinity. At the very limit of sight, an indigo wall stretched from left to right across the north end of the plain. Above it: only sky.

Qiingi found himself standing with his head tilted back, mouth open, looking up and up as the deep blue sky became black overhead. And still the wall they were climbing continued upward as though it cut the universe itself in two.

He had to sit down, clutching the car's rail and trying to steady his breathing. Of course he had known that the world he lived in was a constructed thing; his people were not so foolish as to abandon all true knowledge of their home. But he had been raised not to think of the land this way. Qiingi's understanding was of the habits of fox and otter; he knew the names of all the trees and plants of the forest, and their various properties. Raven's focus was on the human-scale world; that, he claimed, was the only level at which reality could truly make sense to people. Perhaps that was the real reason he was not coming with them.

Yet someone had imagined more. As the elevator rose, faster and faster it seemed as the air thinned, Qiingi tried to enter this manifold, see the world as the coronal's creator must have seen it. He could not Down at the spur, the mountains had seemed like giant waves flinging themselves up Teven Coronal's side wall.

That wall had stretched off into white haze to either side; there was no sense of scale to it. Now as the elevator rose it came clear the wall seemed infinite only if he looked straight up. To either side its distant top became visible, a knife-edge with black above it.

All his life, Qiingi had known the four cardinal directions: if you looked north or south you saw these gigantic walls, but east and west it was different. Far beyond their blurred horizons stood two pillars of up-sweeping blue and white. They curved toward the zenith, narrowing and fading into an ethereal white until they met somewhere behind the suns, an arch bigger than worlds. Qiingi's people called that arch Thunderbird's Door.