I had my doubts as to whether Rialto could protect Lady Agath from an angry wasp, let alone any other threats, but I didn’t feel her to be in any danger, and I didn’t much care if she was, so I left without complaint.

It took me a while to find my way down to the right cellar, but after a few wrong turns I located the place. You can generally tell a wine-cellar by the sturdiness of the door, second only to the treasury door in the majority of castles. Even the most loyal servants will steal your wine given a quarter of a chance, and they’ll piss the evidence over the wall.

I had another trip to find the day cook and get him to unlock for me. He sat on a chair positioned by the door and set to chewing on the leg of mutton he’d carried down with him in his apron.

“Jugs are by the door. Go find what you want. Don’t leave the spigot dripping. Wennith reds are at the far end, left corner, marked with a double cross and crown.”

I lit a lantern from his and ventured in.

“Watch out for spiders,” he said. “The smaller brown ones are bad. Don’t get bit.” When he said “small” he made a circle with his finger and thumb that didn’t look particularly small.

The cellar stretched on for dozens of yards, the wine casks stacked on shelves, most unbroached, the occasional one set with a spigot. I wound a path along the narrow alleys, squeezing past a loading truck and several empty casks left to trip me.

The Wennith red caskets were all sealed save for an empty one. I suspected most of its contents had swilled through the Lady Agath on their way to the privy. The tools and spare spigots for broaching a new cask weren’t apparent. I noted a door, almost concealed beneath a build-up of grime and mould, behind a stack of emptied barrels. It looked too disused to be a store cupboard, but the need of a mallet and spigot provided a good excuse to have a look behind. I’m an explorer at heart and I’d come to nose around in any case. What noble folk keep in their cellars and dungeons can tell you a lot about them. My father kept most of my road-brothers for torture and execution in his dungeon. I won’t say that they didn’t deserve it. Harsh but fair, that’s what my father’s dungeon said about him. Mostly harsh.

I had to lift and heave at the same time to get the door to judder across the flagstones, pushing the empties aside. When a gap had opened large enough to admit me, I went in. A spiral staircase led down. The stairs themselves were carved stone, the work of the castle masons, but the shaft down which they led was poured, Builder-stone. The shaft led down fifty feet or so, into the bedrock. At the bottom an archway led into a rectangular chamber dominated by a grimy machine of cylinders, bolts, and circular plates. Glow-bulbs provided a weak light, three of maybe twenty still working, though not as bright as those in the Tall Castle.

I crossed to the machine and ran a hand along one of its many pipes. My fingers came away black, leaving gleaming streaks of exposed silver metal. The whole machine shook with a faint vibration, little more than heavy footfalls echoing in a stone floor.

“Go away.” An old man stood there, sketched rapidly by an invisible hand. The ghost of an old man I should say, because only light fashioned him. I could see the machine through his body, and he had no colour to his flesh, as if he were made from fog. He wore white clothes, close fitting, of a strange cut, and from one moment to the next his whole form would flicker as if a moth had passed before whatever light was projected to create him.

“Make me,” I said.

“Ha! That’s a good one.” He grinned. In looks he could have been brother to Sword-master Shimon. “Most folk just run screaming when I say ‘boo.’”

“I’ve seen my share of ghosts, old man,” I said.

“Of course you have, boy,” he said. He looked as though he were humouring me. Which was odd given that he was a ghost himself.

“How long have you haunted this place, and what manner of machine is this?” I asked. It pays to be to the point with ghosts and spirits. They tend to vanish before you know it.

“I’m not a ghost. I’m a data echo. The man I am copied from lived another fourteen years after I was captured—”

“How long?”

“—and died more than a thousand years ago,” he said.

“You’re the ghost of a Builder?” I asked. It seemed far-fetched. Even ghosts don’t last that long.

“I am an algorithm. I am portrayed in the image of Fexler Brews, my responses are extrapolated from the six terats of data gathered on the man during the course of his life. I echo him.”

I understood some of the words. “What data? Numbers? Like Qalasadi keeps in his books of trade?”

“Numbers, letters, books, pictures, unguarded moments captured in secret, phrases muttered in his sleep, exclamations cried out in coitus, chemical analysis of his waste, public presentations, private meditations, polygraphic evidence, DNA samples. Data.”

“What can you do for me, ghost?” His gibberish meant little to me. It seemed that they had watched him and written his story into a machine—and now that story spoke to me even though the man himself was dust on the wind.

Fexler Brews shrugged. “I’m an old man out of my time. Not even that. An incomplete copy of an old man out of his time.”

“You can tell me secrets. Give me the power of the ancients,” I said. I didn’t think he would, or my grandfather would already be emperor, but it didn’t hurt to try.

“You wouldn’t understand my secrets. There’s a gap between what I say and what you can comprehend. You people could fill that gap in fifty years if you stopped trying to kill each other and started to look at what’s lying around you.”

“Try me.” I didn’t like his tone. At the end of it this thing before me was nothing but a shadow-play, a story being told by a machine of cogs and springs and magic all bound by the secret fire of the Builders. “What does this do?” I tapped the machinery with my foot. “What is it for?”

Fexler blinked at me. Perhaps he had often blinked so and the machine remembered. “It has many purposes, young man, simple ones that you might understand—the pumping and purification of water—and others that are beyond you. It is a hub, part of a network without end, a tool for observation and communication, bunkered away for security. For me and my kind it serves as one of many windows onto the small world of flesh.”

“Small?” I smiled. He lived in a metal box not much bigger than a coffin.

Fexler frowned, peevish. “I have other things to do: go and play elsewhere.”

“Tell me this,” I said. “My world. It’s not like the one I read about in the oldest books. When they talk about magic, about ghosts, it’s as if they are fairy-tales to frighten children. And yet I have seen the dead walk, seen a boy bring fire with just a thought.”

Fexler frowned as if considering how to explain. “Think of reality as a ship whose course is set, whose wheel is locked in place by universal constants.”

I wondered if a drink would help with such imaginings. All that wine seemed very tempting.

“Our greatest achievement, and downfall, was to turn that wheel, just a fraction. The role of the observer was always important—we discovered that. If a tree falls in the wood and no one hears it, it both does and doesn’t make a sound. If no one sees it, then it is both standing and not standing. The cat is both alive and dead.”