"Let me see the knife," said Iorek Byrnison. "I understand metal. Nothing made of iron or steel is a mystery to a bear. But I have never seen a knife like yours, and I would be glad to look at it closely."

Will and the bear-king were on the foredeck of the river steamer, in the warm rays of the setting sun, and the vessel was making swift progress upstream; there was plenty of fuel on board, there was food that Will could eat, and he and Iorek Byrnison were taking their second measure of each other. They had taken the first already.

Will held out the knife toward Iorek, handle first, and the bear took it from him delicately. His thumb claw opposed the four finger claws, letting him manipulate objects as skillfully as a human, and now he turned the knife this way and that, bringing it closely to his eyes, holding it to catch the light, testing the edge - the steel edge - on a piece of scrap iron.

"This edge is the one you cut my armor with," he said. "The other is very strange. I cannot tell what it is, what it will do, how it was made. But I want to understand it. How did you come to possess it?"

Will told him most of what had happened, leaving out only what concerned him alone: his mother, the man he killed, his father.

"You fought for this, and lost two fingers?" the bear said. "Show me the wound."

Will held out his hand. Thanks to his father's ointment, the raw surfaces were healing well, but they were still very tender. The bear sniffed at them.

"Bloodmoss," he said. "And something else I cannot identify. Who gave you that?"

"A man who told me what I should do with the knife. Then he died. He had some ointment in a horn box, and it cured my wound. The witches tried, but their spell didn't work."

"And what did he tell you to do with the knife?" said Iorek Byrnison, handing it carefully back to Will.

"To use it in a war on the side of Lord Asriel," Will replied. "But first I must rescue Lyra Silvertongue."

"Then we shall help," said the bear, and Will's heart leapt with pleasure.

Over the next few days Will learned why the bears were making this voyage into Central Asia, so far from their homeland.

Since the catastrophe that had burst the worlds open, all the Arctic ice had begun to melt, and new and strange currents appeared in the water. Since the bears depended on ice and on the creatures who lived in the cold sea, they could see that they would soon starve if they stayed where they were; and being rational, they decided how they should respond. They would have to migrate to where there was snow and ice in plenty: they would go to the highest mountains, to the range that touched the sky, half a world away but unshakable, eternal, and deep in snow. From bears of the sea they would become bears of the mountains, for as long as it took the world to settle itself again.

"So you're not making war?" Will said.

"Our old enemies vanished with the seals and the walruses. If we meet new ones, we know how to fight."

"I thought there was a great war coming that would involve everyone. Which side would you fight for in that case?"

"The side that gave advantage to the bears. What else? But I have some regard for a few among humans. One was a man who flew a balloon. He is dead. The other is the witch Serafina Pekkala. The third is the child Lyra Silvertongue. First, I would do whatever serves the bears. Second, whatever serves the child, or the witch, or avenges my dead comrade Lee Scoresby. That is why I will help you rescue Lyra Silvertongue from the abominable woman Coulter."

He told Will of how he and a few of his subjects had swum to the river mouth and paid for the charter of this vessel with gold, and hired the crew, and turned the draining of the Arctic to their own advantage by letting the river take them as far inland as it could - and as it had its source in the northern foothills of the very mountains they sought, and as Lyra was imprisoned there, too, things had fallen out well so far.

So time went past.

During the day Will dozed on deck, resting, gathering strength, because he was exhausted in every part of his being. He watched as the scenery began to change, and the rolling steppe gave way to low grassy hills and then to higher land, with the occasional gorge or cataract; and still the boat steamed south.

He talked to the captain and the crew, out of politeness, but lacking Lyra's instant ease with strangers, he found it difficult to think of much to say; and in any case they were little interested in him. This was only a job, and when it was over they would leave without a backward glance, and besides, they didn't much like the bears, for all their gold. Will was a foreigner, and as long as he paid for his food, they cared little what he did. Besides, there was that strange daemon of his, which seemed so like a witch's: sometimes it was there, and sometimes it seemed to have vanished. Superstitious, like many sailors, they were happy to leave him alone.

Balthamos, for his part, kept quiet, too. Sometimes his grief would become too strong for him to put up with, and he'd leave the boat and fly high among the clouds, searching for any patch of light or taste of air, any shooting stars or pressure ridges that might remind him of experiences he had shared with Baruch. When he talked, at night in the dark of the little cabin Will slept in, it was only to report on how far they had gone, and how much farther ahead the cave and the valley lay. Perhaps he thought Will had little sympathy, though if he'd sought it, he would have found plenty. He became more and more curt and formal, though never sarcastic; he kept that promise, at least.

As for Iorek, he examined the knife obsessively. He looked at it for hours, testing both edges, flexing it, holding it up to the light, touching it with his tongue, sniffing it, and even listening to the sound the air made as it flowed over the surface. Will had no fear for the knife, because Iorek was clearly a craftsman of the highest accomplishment; nor for Iorek himself, because of the delicacy of movement in those mighty paws.

Finally Iorek came to Will and said, "This other edge. It does something you have not told me about. What is it, and how does it work?"

"I can't show you here," said Will, "because the boat is moving. As soon as we stop, I'll show you."

"I can think of it," said the bear, "but not understand what I am thinking. It is the strangest thing I have ever seen."

And he gave it back to Will, with a disconcerting, unreadable long stare out of his deep black eyes.

The river by this time had changed color, because it was meeting the remains of the first floodwaters that had swept down out of the Arctic. The convulsions had affected the earth differently in different places, Will saw; village after village stood up to its roofs in water and hundreds of dispossessed people tried to salvage what they could with rowboats and canoes. The earth must have sunk a little here, because the river broadened and slowed, and it was hard for the skipper to trace his true course through the wide and turbid streams. The air was hotter, and the sun higher in the sky, and the bears found it hard to keep cool; some of them swam alongside as the steamer made its way, tasting their native waters in this foreign land.

But eventually the river narrowed and deepened again, and soon ahead of them began to rise the mountains of the great central Asian plateau. Will saw a rim of white on the horizon one day and watched as it grew and grew, separating itself into different peaks and ridges and passes between them, and so high that it seemed that they must be close at hand - only a few miles. But they were far off still; it was just that the mountains were immense, and with every hour that they came closer, they seemed yet more inconceivably high.

Most of the bears had never seen mountains, apart from the cliffs on their own island of Svalbard, and fell silent as they looked up at the giant ramparts, still so far off.

"What will we hunt there, Iorek Byrnison?" said one. "Are there seals in the mountains? How shall we live?"

"There is snow and ice," was the king's reply. "We shall be comfortable. And there are wild creatures there in plenty. Our lives will be different for a while. But we shall survive, and when things return to what they should be, and the Arctic freezes once more, we shall still be alive to go back and claim it. If we had stayed there, we would have starved. Be prepared for strangeness and for new ways, my bears."

Eventually the steamer could sail no farther, because at this point the riverbed had narrowed and become shallow. The skipper brought the vessel to a halt in a valley bottom that normally would have been carpeted with grass and mountain flowers, where the river would have meandered over gravel beds; but the valley was now a lake, and the captain insisted that he dared not go past it. Beyond this point, he explained, there would be not enough depth below the keel, even with the massive flood from the north.

So they drew up to the edge of the valley, where an outcrop of rock formed a sort of jetty, and disembarked.

"Where are we now?" said Will to the captain, whose English was limited.

The captain found a tattered old map and jabbed at it with his pipe, saying, "This valley here, we now. You take, go on."

"Thank you very much," Will said, and wondered if he ought to offer to pay; but the captain had turned away to supervise the unloading.

Before long all thirty or so bears and all their armor were on the narrow shore. The captain shouted an order, and the vessel began to turn ponderously against the current, maneuvering out into midstream and giving a blast on the whistle that echoed for a long time around the valley.

Will sat on a rock, reading the map. If he was right, the valley where Lyra was captive, according to the shaman, lay some way to the east and the south, and the best way there led through a pass called Sungchen.

"Bears, mark this place," said Iorek Byrnison to his subjects. "When the time comes for us to move back to the Arctic, we shall assemble here. Now go your ways, hunt, feed, and live. Do not make war. We are not here for war. If war threatens, I shall call for you."

The bears were solitary creatures for the most part, and they only came together in times of war or emergency. Now that they were at the edge of a land of snow, they were impatient to be off, each of them, exploring on their own.

"Come, then, Will," said Iorek Byrnison, "and we shall find Lyra."

Will lifted his rucksack and they set off.

It was good walking for the first part of their journey. The sun was warm, but the pines and the rhododendrons kept the worst of the heat off their shoulders, and the air was fresh and clear. The ground was rocky, but the rocks were thick with moss and pine needles, and the slopes they climbed were not precipitous. Will found himself relishing the exercise. The days he had spent on the boat, the enforced rest, had built up his strength. When he had come across Iorek, he had been at the very last of it. He didn't know that, but the bear did.

And as soon as they were alone, Will showed Iorek how the other edge of the knife worked. He opened a world where a tropical rain forest steamed and dripped, and where vapors laden with heavy scent drifted out into the thin mountain air. Iorek watched closely, and touched the edge of the window with his paw, and sniffed at it, and stepped through into the hot, moist air to look around in silence. The monkey shrieks and birdcalls, the insect scrapings and frog croakings, and the incessant drip-drip of condensing moisture sounded very loud to Will, outside it.

Then Iorek came back and watched Will close the window, and asked to see the knife again, peering so closely at the silver edge that Will thought he was in danger of cutting his eye. He examined it for a long time and handed it back with hardly a word, only saying, "I was right: I could not have fought this."

They moved on, speaking little, which suited them both, Iorek Byrnison caught a gazelle and ate most of it, leaving the tender meat for Will to cook; and once they came to a village, and while Iorek waited in the forest, Will exchanged one of his gold coins for some flat, coarse bread and some dried fruit, and for boots of yak leather and a waistcoat of a kind of sheepskin, for it was becoming cold at night.

He also managed to ask about the valley with the rainbows. Balthamos helped by assuming the form of a crow, like the daemon of the man Will was speaking to; he made the passage of understanding easier between them, and Will got directions, which were helpful and clear.

It was another three days' walk. Well, they were getting there. And so were others.

Lord Asriel's force, the squadron of gyropters and the zeppelin fuel tanker, had reached the opening between the worlds: the breach in the sky above Svalbard. They had a very long way to go still, but they flew without pause except for essential maintenance, and the commander, the Afric King Ogunwe, kept in twice-daily touch with the basalt fortress. He had a Gallivespian lodestone operator aboard his gyropter, and through him he was able to learn as quickly as Lord Asriel himself about what was going on elsewhere.

The news was disconcerting. The little spy, the Lady Salmakia, had watched from the shadows as the two powerful arms of the Church, the Consistorial Court of Discipline and the Society of the Work of the Holy Spirit, agreed to put their differences aside and pool their knowledge. The Society had a swifter and more skillful alethiometrist than Fra Pavel, and thanks to him, the Consistorial Court now knew exactly where Lyra was, and more: they knew that Lord Asriel had sent a force to rescue her. Wasting no time, the Court commandeered a flight of zeppelins, and that same day a battalion of the Swiss Guard began to embark aboard the zeppelins waiting in the still air beside the Lake of Geneva.

So each side was aware that the other was also making its way toward the cave in the mountains. And they both knew that whoever got there first would have the advantage, but there wasn't much in it: Lord Asriel's gyropters were faster than the zeppelins of the Consistorial Court, but they had farther to fly, and they were limited by the speed of their own zeppelin tanker.

And there was another consideration: whoever seized Lyra first would have to fight their way out against the other force. It would be easier for the Consistorial Court, because they didn't have to consider getting Lyra away safely. They were flying there to kill her. The zeppelin carrying the President of the Consistorial Court was carrying other passengers as well, unknown to him. The Chevalier Tialys had received a message on his lodestone resonator, ordering him and the Lady Salmakia to smuggle themselves aboard. When the zeppelins arrived at the valley, he and the Lady were to go ahead and make their way independently to the cave where Lyra was held, and protect her as well as they could until King Ogunwe's force arrived to rescue her. Her safety was to come above every other consideration.

Getting themselves aboard the zeppelin was hazardous for the spies, not least because of the equipment they had to carry. Apart from the lodestone resonator, the most important items were a pair of insect larvae, and their food. When the adult insects emerged, they would be more like dragon-flies than anything else, but they were not like any kind of dragonfly that the humans of Will's world, or Lyra's, would have seen before. They were very much larger, for one thing. The Gallivespians bred these creatures carefully, and each clan's insects differed from the rest. The Chevalier Tialys's clan bred powerful red-and-yellow-striped dragonflies with vigorous and brutal appetites, whereas the one the Lady Salmakia was nurturing would be a slender, fast-flying creature with an electric blue body and the power of glowing in the dark.

Every spy was equipped with a number of these larvae, which, by feeding them carefully regulated amounts of oil and honey, they could either keep in suspended animation or bring rapidly to adulthood. Tialys and Salmakia had thirty-six hours, depending on the winds, to hatch these larvae now - because that was about the time the flight would take, and they needed the insects to emerge before the zeppelins landed.

The Chevalier and his colleague found an overlooked space behind a bulkhead, and made themselves as safe as they could while the vessel was loaded and fueled; and then the engines began to roar, shaking the light structure from end to end as the ground crew cast off and the eight zeppelins rose into the night sky.

Their kind would have regarded the comparison as a mortal insult, but they were able to conceal themselves at least as well as rats. From their hiding place, the Gallivespians could overhear a good deal, and they kept in hourly touch with Lord Roke, who was aboard King Ogunwe's gyropter.

But there was one thing they couldn't learn any more about on the zeppelin, because the President never spoke of it: and that was the matter of the assassin, Father Gomez, who had been absolved already of the sin he was going to commit if the Consistorial Court failed in their mission. Father Gomez was somewhere else, and no one was tracking him at all.