But among them all there were some he felt more easily than others, and, already knowing the answer, he cut one through to be sure: his own world again.

He closed it up and felt with the knife tip for a snag with a different quality. He found one that was elastic and resistant, and let the knife feel its way through.

And yes! The world he saw through that window was not his own: the ground was closer here, and the landscape was not green fields and hedges but a desert of rolling dunes.

He closed it and opened another: the smoke-laden air over an industrial city, with a line of chained and sullen workers trudging into a factory.

He closed that one, too, and came back to himself. He felt a little dizzy. For the first time he understood some of the true power of the knife, and laid it very carefully on the rock in front of him.

"Are you going to stay here all day?" said Balthamos.

"I’m thinking. You can only move easily from one world to another if the ground’s in the same place. And maybe there are places where it is, and maybe that’s where a lot of cutting-through happens… And you’d have to know what your own world felt like with the point or you might never get back. You’d be lost forever."

"Indeed. But may we—"

"And you’d have to know which world had the ground in the same place, or there wouldn’t be any point in opening it," said Will, as much to himself as to the angel. "So it’s not as easy as I thought. We were just lucky in Oxford and Cittàgazze, maybe. But I’ll just…"

He picked up the knife again. As well as the clear and obvious feeling he got when he touched a point that would open to his own world, there had been another kind of sensation he’d touched more than once: a quality of resonance, like the feeling of striking a heavy wooden drum, except of course that it came, like every other one, in the tiniest movement through the empty air.

There it was. He moved away and felt somewhere else: there it was again.

He cut through and found that his guess was right. The resonance meant that the ground in the world he’d opened was in the same place as this one. He found himself looking at a grassy upland meadow under an overcast sky, in which a herd of placid beasts was grazing—animals such as he’d never seen before—creatures the size of bison, with wide horns and shaggy blue fur and a crest of stiff hair along their backs.

He stepped through. The nearest animal looked up incuriously and then turned back to the grass. Leaving the window open, Will, in the other-world meadow, felt with the knifepoint for the familiar snags and tried them.

Yes, he could open his own world from this one, and he was still high above the farms and hedges; and yes, he could easily find the solid resonance that meant the Cittàgazze-world he’d just left.

With a deep sense of relief, Will went back to the camp by the lake, closing everything behind him. Now he could find his way home; now he would not get lost; now he could hide when he needed to, and move about safely.

With every increase in his knowledge came a gain in strength. He sheathed the knife at his waist and swung the rucksack over his shoulder.

"Well, are you ready now?" said that sarcastic voice.

"Yes. I’ll explain if you like, but you don’t seem very interested."

"Oh, I find whatever you do a source of perpetual fascination. But never mind me. What are you going to say to these people who are coming?"

Will looked around, startled. Farther down the trail—a long way down—there was a line of travelers with packhorses, making their way steadily up toward the lake. They hadn’t seen him yet, but if he stayed where he was, they would soon.

Will gathered up his father’s cloak, which he’d laid over a rock in the sun. It weighed much less now that it was dry. He looked around: there was nothing else he could carry.

"Let’s go farther on," he said.

He would have liked to retie the bandage, but it could wait. He set off along the edge of the lake, away from the travelers, and the angel followed him, invisible in the bright air.

Much later that day they came down from the bare mountains onto a spur covered in grass and dwarf rhododendrons. Will was aching for rest, and soon, he decided, he’d stop.

He’d heard little from the angel. From time to time Balthamos had said, "Not that way," or "There is an easier path to the left," and he’d accepted the advice; but really he was moving for the sake of moving, and to keep away from those travelers, because until the other angel came back with more news, he might as well have stayed where they were.

Now the sun was setting, he thought he could see his strange companion. The outline of a man seemed to quiver in the light, and the air was thicker inside it.

"Balthamos?" he said. "I want to find a stream. Is there one nearby?"

"There is a spring halfway down the slope," said the angel, "just above those trees."

"Thank you," said Will.

He found the spring and drank deeply, filling his canteen. But before he could go on down to the little wood, there came an exclamation from Balthamos, and Will turned to see his outline dart across the slope toward—what? The angel was visible only as a flicker of movement, and Will could see him better when he didn’t look at him directly; but he seemed to pause, and listen, and then launch himself into the air to skim back swiftly to Will.

"Here!" he said, and his voice was free of disapproval and sarcasm for once. "Baruch came this way! And there is one of those windows, almost invisible. Come—come. Come now."

Will followed eagerly, his weariness forgotten. The window, he saw when he reached it, opened onto a dim, tundra-like landscape that was flatter than the mountains in the Cittàgazze world, and colder, with an overcast sky. He went through, and Balthamos followed him at once.

"Which world is this?" Will said.

"The girl’s own world. This is where they came through. Baruch has gone ahead to follow them."

"How do you know? Do you read his mind?"

"Of course I read his mind. Wherever he goes, my heart goes with him; we feel as one, though we are two."

Will looked around. There was no sign of human life, and the chill in the air was increasing by the minute as the light failed.

"I don’t want to sleep here," he said. "We’ll stay in the C’gazze world for the night and come through in the morning. At least there’s wood back there, and I can make a fire. And now I know what her world feels like, I can find it with the knife… Oh, Balthamos? Can you take any other shape?"

"Why would I wish to do that?"

"In this world human beings have daemons, and if I go about without one, they’ll be suspicious. Lyra was frightened of me at first because of that. So if we’re going to travel in her world, you’ll have to pretend to be my daemon, and take the shape of some animal. A bird, maybe. Then you could fly, at least."

"Oh, how tedious."

"Can you, though?"

"I could…"

"Do it now, then. Let me see."

The form of the angel seemed to condense and swirl into a little vortex in midair, and then a blackbird swooped down onto the grass at Will’s feet.

"Fly to my shoulder," said Will.

The bird did so, and then spoke in the angel’s familiar acid tone:

"I shall only do this when it’s absolutely necessary. It’s unspeakably humiliating."

"Too bad," said Will. "Whenever we see people in this world, you become a bird. There’s no point in fussing or arguing. Just do it."

The blackbird flew off his shoulder and vanished in midair, and there was the angel again, sulking in the half-light. Before they went back through, Will looked all around, sniffing the air, taking the measure of the world where Lyra was captive.

"Where is your companion now?" he said.