He moved on down the slope, cheered.

It took three hours, and several words of guidance, before he came to the little blue lake. By the time he reached it, he was parched with thirst, and in the baking sun the cloak was heavy and hot—though when he took it off, he missed its cover, for his bare arms and neck were soon burning. He dropped cloak and rucksack and ran the last few yards to the water, to fall on his face and swallow mouthful after freezing mouthful. It was so cold that it made his teeth and skull ache.

Once he’d slaked the thirst, he sat up and looked around. He’d been in no condition to notice things the day before, but now he saw more clearly the intense color of the water, and heard the strident insect noises from all around.

"Balthamos?"

"Always here."

"Where is the dead man?"

"Beyond the high rock on your right."

"Are there any Specters around?"

"No, none. I don’t have anything the Specters want, and nor have you."

Will took up his rucksack and cloak and made his way along the edge of the lake and up onto the rock Balthamos had pointed out.

Beyond it a little camp had been set up, with five or six tents and the remains of cooking fires. Will moved down warily in case there was someone still alive and hiding.

But the silence was profound, with the insect scrapings only scratching at the surface of it. The tents were still, the water was placid, with the ripples still drifting slowly out from where he’d been drinking. A flicker of green movement near his foot made him start briefly, but it was only a tiny lizard.

The tents were made of camouflage material, which only made them stand out more among the dull red rocks. He looked in the first and found it empty. So was the second, but in the third he found something valuable: a mess tin and a box of matches. There was also a strip of some dark substance as long and as thick as his forearm. At first he thought it was leather, but in the sunlight he saw it clearly to be dried meat.

Well, he had a knife, after all. He cut a thin sliver and found it chewy and very slightly salty, but full of good flavor. He put the meat and the matches together with the mess tin into his rucksack and searched the other tents, but found them empty.

He left the largest till last.

"Is that where the dead man is?" he said to the air.

"Yes," said Balthamos. "He has been poisoned."

Will walked carefully around to the entrance, which faced the lake. Sprawled beside an overturned canvas chair was the body of the man known in Will’s world as Sir Charles Latrom, and in Lyra’s as Lord Boreal, the man who stole her alethiometer, which theft in turn led Will to the subtle knife itself. Sir Charles had been smooth, dishonest, and powerful, and now he was dead. His face was distorted unpleasantly, and Will didn’t want to look at it, but a glance inside the tent showed that there were plenty of things to steal, so he stepped over the body to look more closely.

His father, the soldier, the explorer, would have known exactly what to take. Will had to guess. He took a small magnifying glass in a steel case, because he could use it to light fires and save his matches; a reel of tough twine; an alloy canteen for water, much lighter than the goatskin flask he had been carrying, and a small tin cup; a small pair of binoculars; a roll of gold coins the size of a man’s thumb, wrapped in paper; a first-aid kit; water-purifying tablets; a packet of coffee; three packs of compressed dried fruit; a bag of oatmeal biscuits; six bars of Kendal Mint Cake; a packet of fishhooks and nylon line; and finally, a notebook and a couple of pencils, and a small electric torch.

He packed it all in his rucksack, cut another sliver of meat, filled his belly and then his canteen from the lake, and said to Balthamos:

"Do you think I need anything else?"

"You could do with some sense," came the reply. "Some faculty to enable you to recognize wisdom and incline you to respect and obey it."

"Are you wise?"

"Much more so than you."

"Well, you see, I can’t tell. Are you a man? You sound like a man."

"Baruch was a man. I was not. Now he is angelic."

"So—" Will stopped what he was doing, which was arranging his rucksack so the heaviest objects were in the bottom, and tried to see the angel. There was nothing there to see. "So he was a man," he went on, "and then… Do people become angels when they die? Is that what happens?"

"Not always. Not in the vast majority of cases… Very rarely."

"When was he alive, then?"

"Four thousand years ago, more or less. I am much older."

"And did he live in my world? Or Lyra’s? Or this one?"

"In yours. But there are myriads of worlds. You know that."

"But how do people become angels?"

"What is the point of this metaphysical speculation?"

"I just want to know."

"Better to stick to your task. You have plundered this dead man’s property, you have all the toys you need to keep you alive; now may we move on?"

"When I know which way to go."

"Whichever way we go, Baruch will find us."

"Then he’ll still find us if we stay here. I’ve got a couple more things to do."

Will sat down where he couldn’t see Sir Charles’s body and ate three squares of the Kendal Mint Cake. It was wonderful how refreshed and strengthened he felt as the food began to nourish him. Then he looked at the alethiometer again. The thirty-six little pictures painted on ivory were each perfectly clear: there was no doubt that this was a baby, that a puppet, this a loaf of bread, and so on. It was what they meant that was obscure.

"How did Lyra read this?" he said to Balthamos.

"Quite possibly she made it up. Those who use these instruments have studied for many years, and even then they can only understand them with the help of many books of reference."

"She wasn’t making it up. She read it truly. She told me things she could never have known otherwise."

"Then it is as much of a mystery to me, I assure you," said the angel.

Looking at the alethiometer, Will remembered something Lyra had said about reading it: something about the state of mind she had to be in to make it work. It had helped him, in turn, to feel the subtleties of the silver blade.

Feeling curious, he took out the knife and cut a small window in front of where he was sitting. Through it he saw nothing but blue air, but below, far below, was a landscape of trees and fields: his own world, without a doubt.

So mountains in this world didn’t correspond to mountains in his. He closed the window, using his left hand for the first time. The joy of being able to use it again!

Then an idea came to him so suddenly it felt like an electric shock.

If there were myriads of worlds, why did the knife only open windows between this one and his own?

Surely it should cut into any of them.

He held it up again, letting his mind flow along to the very tip of the blade as Giacomo Paradisi had told him, until his consciousness nestled among the atoms themselves and he felt every tiny snag and ripple in the air.

Instead of cutting as soon as he felt the first little halt, as he usually did, he let the knife move on to another and another. It was like tracing a row of stitches while pressing so softly that none of them was harmed.

"What are you doing?" said the voice from the air, bringing him back.

"Exploring," said Will. "Be quiet and keep out of the way. If you come near this you’ll get cut, and if I can’t see you, I can’t avoid you."

Balthamos made a sound of muted discontent. Will held out the knife again and felt for those tiny halts and hesitations.

There were far more of them than he’d thought. And as he felt them without the need to cut through at once, he found that they each had a different quality: this one was hard and definite, that one cloudy; a third was slippery, a fourth brittle and frail…