At that moment the Gallivespians, too, were talking about the knife. Having made a suspicious peace with Iorek Byrnison, they climbed back to their ledge to be out of the way, and as the crackle of flames rose and the snapping and roaring of the fire filled the air, Tialys said, "We must never leave his side. As soon as the knife is mended, we must keep closer than a shadow."

"He is too alert. He watches everywhere for us," said Salmakia. "The girl is more trusting. I think we could win her around. She's innocent, and she loves easily. We could work on her. I think we should do that, Tialys."

"But he has the knife. He is the one who can use it."

"He won't go anywhere without her."

"But she has to follow him, if he has the knife. And I think that as soon as the knife's intact again, they'll use it to slip into another world, so as to get away from us. Did you see how he stopped her from speaking when she was going to say something more? They have some secret purpose, and it's very different from what we want them to do."

"We'll see. But you're right, Tialys, I think. We must stay close to the boy at all costs."

They both watched with some skepticism as Iorek Byrnison laid out the tools in his improvised workshop. The mighty workers in the ordnance factories under Lord Asriel's fortress, with their blast furnaces and rolling mills, their anbaric forges and hydraulic presses, would have laughed at the open fire, the stone hammer, the anvil consisting of a piece of Iorek's armor. Nevertheless, the bear had taken the measure of the task, and in the certainty of his movements the little spies began to see some quality that muffled their scorn.

When Lyra and Will came in with the bushes, Iorek directed them in placing branches carefully on the fire. He looked at each branch, turning it from side to side, and then told Will or Lyra to place it at such-and-such an angle, or to break off part and place it separately at the edge. The result was a fire of extraordinary ferocity, with all its energy concentrated at one side.

By this time the heat in the cave was intense. Iorek continued to build the fire, and made the children take two more trips down the path to ensure that there was enough fuel for the whole operation.

Then the bear turned over a small stone on the floor and told Lyra to find some more stones of the same kind. He said that those stones, when heated, gave off a gas that would surround the blade and keep the air from it, for if the hot metal came in contact with the air, it would absorb some and be weakened by it.

Lyra set about searching, and with owl-eyed Pantalaimon's help soon had a dozen or more stones to hand. Iorek told her how to place them, and where, and showed her exactly the kind of draft she should get moving, with a leafy branch, to make sure the gas flowed evenly over the work piece.

Will was placed in charge of the fire, and Iorek spent several minutes directing him and making sure he understood the principles he was to use. So much depended on exact placement, and Iorek could not stop and correct each one; Will had to understand, and then he'd do it properly.

Furthermore, he mustn't expect the knife to look exactly the same when it was mended. It would be shorter, because each section of the blade would have to overlap the next by a little way so they could be forged together; and the surface would have oxidized a little, despite the stone-gas, so some of the play of color would be lost; and no doubt the handle would be charred. But the blade would be just as sharp, and it would work.

So Will watched as the flames roared along the resinous twigs, and with streaming eyes and scorched hands he adjusted each fresh branch till the heat was focused as Iorek wanted it.

Meanwhile, Iorek himself was grinding and hammering a fist-sized stone, having rejected several until he found one of the right weight. With massive blows he shaped it and smoothed it, the cordite smell of smashed rocks joining the smoke in the nostrils of the two spies, watching from high up. Even Pantalaimon was active, changing to a crow so he could flap his wings and make the fire burn faster.

Eventually the hammer was formed to Iorek's satisfaction, and he set the first two pieces of the blade of the subtle knife among the fierce-burning wood at the heart of the fire, and told Lyra to begin wafting the stone-gas over them. The bear watched, his long white face lurid in the glare, and Will saw the surface of the metal begin to glow red and then yellow and then white.

Iorek was watching closely, his paw held ready to snatch the pieces out. After a few moments the metal changed again, and the surface became shiny and glistening, and sparks just like those from a firework sprayed up from it.

Then Iorek moved. His right paw darted in and seized first one piece and then the other, holding them between the tips of his massive claws and placing them on the slab of iron that was the backplate of his armor. Will could smell the claws burning, but Iorek took no notice of that, and moving with extraordinary speed he adjusted the angle at which the pieces overlapped and then raised his left paw high and struck a blow with the rock hammer.

The knife tip leapt on the rock under the massive blow. Will was thinking that the whole of the rest of his life depended on what happened in that tiny triangle of metal, that point that searched out the gaps inside the atoms, and all his nerves trembled, sensing every flicker of every flame and the loosening of every atom in the lattice of the metal. Before this began, he had supposed that only a full-scale furnace, with the finest tools and equipment, could work on that blade; but now he saw that these were the finest tools, and that Iorek's artistry had constructed the best furnace there could be.

Iorek roared above the clangor, "Hold it still in your mind! You have to forge it, too! This is your task as much as mine!"

Will felt his whole being quiver under the blows of the stone hammer in the bear's fist. The second piece of the blade was heating, too, and Lyra's leafy branch sent the hot gas along to bathe both pieces in its flow and keep out the iron-eating air. Will sensed it all and felt the atoms of the metal linking each to each across the fracture, forming new crystals again, strengthening and straightening themselves in the invisible lattice as the join came good.

"The edge!" roared Iorek. "Hold the edge in line!"

He meant with your mind, and Will did it instantly, sensing the minute snags and then the minute easement as the edges lined up perfectly. Then that join was made, and Iorek turned to the next piece.

"A new stone," he called to Lyra, who knocked the first one aside and placed a second on the spot to heat.

Will checked the fuel and snapped a branch in two to direct the flames better, and Iorek began to work with the hammer once more. Will felt a new layer of complexity added to his task, because he had to hold the new piece in a precise relation with both the previous two, and he understood that only by doing that accurately could he help Iorek mend it.

So the work continued. He had no idea how long it took; Lyra, for her part, found her arms aching, her eyes streaming, her skin scorched and red, and every bone in her body aching with fatigue; but still she placed each stone as Iorek had told her, and still the weary Pantalaimon raised his wings readily and beat them over the flames.

When it came to the final join, Will's head was ringing, and he was so exhausted by the intellectual effort he could barely lift the next branch onto the fire. He had to understand every connection, or the knife would not hold together. And when it came to the most complex one, the last, which would affix the nearly finished blade onto the small part remaining at the handle, if he couldn't hold it in his full consciousness together with all the others, then the knife would simply fall apart as if Iorek had never begun.

The bear sensed this, too, and paused before he began heating the last piece. He looked at Will, and in his eyes Will could see nothing, no expression, just a bottomless black brilliance. Nevertheless, he understood: this was work, and it was hard, but they were equal to it, all of them.

That was enough for Will, so he turned back to the fire and sent his imagination out to the broken end of the haft, and braced himself for the last and fiercest part of the task.

So he and Iorek and Lyra together forged the knife, and how long the final join took he had no idea; but when Iorek had struck the final blow, and Will had felt the final tiny settling as the atoms connected across the break, Will sank down onto the floor of the cave and let exhaustion possess him. Lyra nearby was in the same state, her eyes glassy and red-rimmed, her hair full of soot and smoke; and Iorek himself stood heavy-headed, his fur singed in several places, dark streaks of ash marking its rich cream-white.

Tialys and Salmakia had slept in turns, one of them always alert. Now she was awake and he was sleeping, but as the blade cooled from red to gray and finally to silver, and as Will reached out for the handle, she woke her partner with a hand on his shoulder. He was alert at once.

But Will didn't touch the knife: he held his palm close by, and the heat was still too great for his hand. The spies relaxed on the rocky shelf as Iorek said to Will:

"Come outside."

Then he said to Lyra: "Stay here, and don't touch the knife."

Lyra sat close to the anvil, where the knife lay cooling, and Iorek told her to bank the fire up and not let it burn down: there was a final operation yet.

Will followed the great bear out onto the dark mountainside. The cold was bitter and instantaneous, after the inferno in the cave.

"They should not have made that knife," said Iorek, after they had walked a little way. "Maybe I should not have mended it. I'm troubled, and I have never been troubled before, never in doubt. Now I am full of doubt. Doubt is a human thing, not a bear thing. If I am becoming human, something's wrong, something's bad. And I've made it worse."

"But when the first bear made the first piece of armor, wasn't that bad, too, in the same way?"

Iorek was silent. They walked on till they came to a big drift of snow, and Iorek lay in it and rolled this way and that, sending flurries of snow up into the dark air, so that it looked as if he himself were made of snow, he was the personification of all the snow in the world.

When he was finished, he rolled over and stood up and shook himself vigorously, and then, seeing Will still waiting for an answer to his question, said:

"Yes, I think it might have been, too. But before that first armored bear, there were no others. We know of nothing before that. That was when custom began. We know our customs, and they are firm and solid and we follow them without change. Bear nature is weak without custom, as bear flesh is unprotected without armor.

"But I think I have stepped outside bear nature in mending this knife. I think I've been as foolish as lofur Rakinson. Time will tell. But I am uncertain and doubtful. Now you must tell me: ............