Once the mulefa began to build the platform for Mary, they worked quickly and well. She enjoyed watching them, because they could discuss without quarreling and cooperate without getting in each other's way, and because their techniques of splitting and cutting and joining wood were so elegant and effective.

Within two days the observation platform was designed and built and lifted into place. It was firm and spacious and comfortable, and when she had climbed up to it, she was as happy, in one way, as she had ever been. That one way was physically. In the dense green of the canopy, with the rich blue of the sky between the leaves; with a breeze keeping her skin cool, and the faint scent of the flowers delighting her whenever she sensed it; with the rustle of the leaves, the song of the hundreds of birds, and the distant murmur of the waves on the seashore, all her senses were lulled and nurtured, and if she could have stopped thinking, she would have been entirely lapped in bliss.

But of course thinking was what she was there for.

And when she looked through her spyglass and saw the relentless outward drift of the sraf, the shadow particles, it seemed to her as if happiness and life and hope were drifting away with them. She could find no explanation at all.

Three hundred years, the mulefa had said: that was how long the trees had been failing. Given that the shadow particles passed through all the worlds alike, presumably the same thing was happening in her universe, too, and in every other one. Three hundred years ago, the Royal Society was set up: the first true scientific society in her world. Newton was making his discoveries about optics and gravitation.

Three hundred years ago in Lyra's world, someone invented the alethiometer.

At the same time in that strange world through which she'd come to get here, the subtle knife was invented.

She lay back on the planks, feeling the platform move in a very slight, very slow rhythm as the great tree swayed in the sea breeze. Holding the spyglass to her eye, she watched the myriad tiny sparkles drift through the leaves, past the open mouths of the blossoms, through the massive boughs, moving against the wind, in a slow, deliberate current that looked all but conscious.

What had happened three hundred years ago? Was it the cause of the Dust current, or was it the other way around? Or were they both the results of a different cause altogether? Or were they simply not connected at all?

The drift was mesmerizing. How easy it would be to fall into a trance, and let her mind drift away with the floating particles...

Before she knew what she was doing, and because her body was lulled, that was exactly what happened. She suddenly snapped awake to find herself outside her body, and she panicked.

She was a little way above the platform, and a few feet off among the branches. And something had happened to the Dust wind: instead of that slow drift, it was racing like a river in flood. Had it sped up, or was time moving differently for her, now that she was outside her body? Either way she was conscious of the most horrible danger, because the flood was threatening to sweep her loose completely, and it was immense. She flung out her arms to seize hold of anything solid - but she had no arms. Nothing connected. Now she was almost over that abominable drop, and her body was farther and farther from reach, sleeping so hoggishly below her. She tried to shout and wake herself up: not a sound. The body slumbered on, and the self that observed was being borne away out of the canopy of leaves altogether and into the open sky.

And no matter how she struggled, she could make no headway. The force that carried her out was as smooth and powerful as water pouring over a weir; the particles of Dust were streaming along as if they, too, were pouring over some invisible edge.

And carrying her away from her body.

She flung a mental lifeline to that physical self, and tried to recall the feeling of being in it: all the sensations that made up being alive. The exact touch of her friend Atal's soft-tipped trunk caressing her neck. The taste of bacon and eggs. The triumphant strain in her muscles as she pulled herself up a rock face. The delicate dancing of her fingers on a computer keyboard. The smell of roasting coffee. The warmth of her bed on a winter night.

And gradually she stopped moving; the lifeline held fast, and she felt the weight and strength of the current pushing against her as she hung there in the sky.

And then a strange thing happened. Little by little (as she reinforced those sense-memories, adding others, tasting an iced margarita in California, sitting under the lemon trees outside a restaurant in Lisbon, scraping the frost off the windshield of her car), she felt the Dust wind easing. The pressure was lessening.

But only on her: all around, above and below, the great flood was streaming as fast as ever. Somehow there was a little patch of stillness around her, where the particles were resisting the flow.

They were conscious! They felt her anxiety and responded to it. And they began to carry her back to her deserted body, and when she was close enough to see it once more, so heavy, so warm, so safe, a silent sob convulsed her heart.

And then she sank back into her body and awoke.

She took in a shuddering deep breath. She pressed her hands and her legs against the rough planks of the platform, and having a minute ago nearly gone mad with fear, she was now suffused with a deep, slow ecstasy at being one with her body and the earth and everything that was matter.

Finally she sat up and tried to take stock. Her fingers found the spyglass, and she held it to her eye, supporting one trembling hand with the other. There was no doubt about it: that slow sky-wide drift had become a flood. There was nothing to hear and nothing to feel, and without the spyglass, nothing to see, but even when she took the glass from her eye, the sense of that swift, silent inundation remained vividly, together with something she hadn't noticed in the terror of being outside her body: the profound, helpless regret that was abroad in the air.

The shadow particles knew what was happening and were sorrowful.

And she herself was partly shadow matter. Part of her was subject to this tide that was moving through the cosmos. And so were the mulefa, and so were human beings in every world, and every kind of conscious creature, wherever they were.

And unless she found out what was happening, they might all find themselves drifting away to oblivion, everyone.

Suddenly she longed for the earth again. She put the spyglass in her pocket and began the long climb down to the ground.

Father Gomez stepped through the window as the evening light lengthened and mellowed. He saw the great stands of wheel trees and the roads lacing through the prairie, just as Mary had done from the same spot sometime before. But the air was free of haze, for it had rained a little earlier, and he could see farther than she had; in particular, he could see the glimmer of a distant sea and some flickering white shapes that might be sails.

He lifted the rucksack higher on his shoulders and turned toward them to see what he could find. In the calm of the long evening, it was pleasant to walk on this smooth road, with the sound of some cicada-like creatures in the long grass and the setting sun warm in his face. The air was fresh, too, clear and sweet and entirely free of the taint of naphtha fumes, kerosene fumes, whatever they were, which had lain so heavily on the air in one of the worlds he'd passed through: the world his target, the tempter herself, belonged to.

He came out at sunset on a little headland beside a shallow bay. If they had tides in this sea, the tide was high, because there was only a narrow fringe of soft white sand above the water.

And floating in the calm bay were a dozen or more. Father Gomez had to stop and think carefully. A dozen or more enormous snow-white birds, each the size of a rowboat, with long, straight wings that trailed on the water behind them: very long wings, at least two yards in length. Were they birds? They had feathers, and heads and beaks not unlike swans', but those wings were situated one in front of the other, surely...

Suddenly they saw him. Heads turned with a snap, and at once all those wings were raised high, exactly like the sails of a yacht, and they all leaned in with the breeze, making for the shore.

Father Gomez was impressed by the beauty of those wing-sails, by how they were flexed and trimmed so perfectly, and by the speed of the birds. Then he saw that they were paddling, too: they had legs under the water, placed not fore and aft like the wings but side by side, and with the wings and the legs together, they had an extraordinary speed and grace in the water.

As the first one reached the shore, it lumbered up through the dry sand, making directly for the priest. It was hissing with malice, stabbing its head forward as it waddled heavily up the shore, and the beak snapped and clacked. There were teeth in the beak, too, like a series of sharp incurved hooks.

Father Gomez was about a hundred yards from the edge of the water, on a low grassy promontory, and he had plenty of time to put down his rucksack, take out the rifle, load, aim, and fire.

The bird's head exploded in a mist of red and white, and the creature blundered on clumsily for several steps before sinking onto its breast. It didn't die for a minute or more; the legs kicked, the wings rose and fell, and the great bird beat itself around and around in a bloody circle, kicking up the rough grass, until a long, bubbling expiration from its lungs ended with a coughing spray of red, and it fell still.

The other birds had stopped as soon as the first one fell, and stood watching it, and watching the man, too. There was a quick, ferocious intelligence in their eyes. They looked from him to the dead bird, from that to the rifle, from the rifle to his face.

He raised the rifle to his shoulder again and saw them react, shifting backward clumsily, crowding together. They understood.

They were fine, strong creatures, large and broad-backed - like living boats, in fact. If they knew what death was, thought Father Gomez, and if they could see the connection between death and himself, then there was the basis of a fruitful understanding between them. Once they had truly learned to fear him, they would do exactly as he said.