Scrivener's Moon by Philip Reeve

nightwights , my Lord Mayor?”
    Quercus said, “If you really think there is valuable old-tech in this pyramid, we could send another Engineer. Steepleton, or Lark.”
    “Lord Mayor, did I not explain? This place may have been made by the first Stalker builders. We might find Stalker brains there, which would be useful enough, since we have no spares left, and our Stalkers are wearing out at a frightening rate. Or we may find something better: the secret of making Stalker brains for ourselves; the answer to the mystery of how the Stalkers are powered. You think the new London is mighty now? Imagine how much mightier it would be if you could power it by Molecular Clockwork!”
    Quercus said nothing.
    “How many Stalkers do we have left now?” asked Wavey. “Fifty, is it?”
    “Fifty-six. Another sixty in the north with Rufus Raven’s Lazarus Brigade.”
    “Well there you go. You could do with some more, I’m sure. Steepleton and Lark know nothing about Stalkers. I am the only one qualified to investigate this site. If you lend me a landship I could be there and back in a few weeks and bring home all sorts of wonders. Dr Crumb and his colleagues are perfectly capable of continuing the work on London while I am away.”
    Quercus scratched his chin and studied the map.
    “If I don’t go there, someone else will,” Wavey warned. “Native taboos may keep nomads and snowmads away, but news that the tower is open is sure to spread. When it does, adventurers from Paris and Hamsterdam and Bremen will set off, hoping to secure its secrets for their cities.”
    Those three cities were London’s main rivals. They had scoffed at Quercus’s plan when it was first announced, but now they were growing worried; in the past year they had all stopped selling steel and other raw materials to London. Paris was rumoured to be building a huge chassis of its own.
    “Very well,” said Quercus suddenly. That was his way; he considered things deeply, made decisions swiftly, and stuck to them. “Take a landship, and my blessing. Dr Crumb will serve as Acting Chief Engineer in your absence. We shall tell no one your real reason for going.”
    Wavey smiled in the calm, contented way she always did when she had just got something that she wanted. “I shall set out with Master Borglum. We can tell people that I am going to visit friends in the north.”
    Dr Crumb started to protest again. He had never been further north of London than his old childhood home at Lesser Wintermire, and Lesser Wintermire had been quite bad enough. The far north was a wild place, where science and reason were unknown. But he had never been able to get his own way with Wavey, not since that first long-ago day when she decided that he was to be her lover, and he didn’t now: she hushed him, and she and Quercus began discussing arrangements and the best route north.
    Fever went to the window. The rain was still falling. Out in the sodden street a passing apprentice Engineer paused to peer at the house, probably wondering why the Lord Mayor’s chair and bodyguards were waiting outside. She caught his glance, his eyes dark as charcoal smudges. Charley Shallow . . . Why did that boy always make her feel guilty? she wondered. It wasn’t as if she had tried to murder him . . .
    He saw her watching him and went hurrying on his way, trying to pretend that he had not been looking at the house at all.
    It wasn’t his fault, Fever decided. It was just London, so dingy and crowded, so full of upsetting memories. She felt caged here; had felt it ever since they brought her home from Mayda. A view opened in her mind of worldwide moors under a high sky; curlews calling, ice on the skyline like a long white wave, curtains of light dancing in the dusk. She could almost see Skrevanastuut itself; a black pyramid on a bare hill. North. Even the word sounded clean and free.
    She turned, and her mother stopped talking and looked up expectantly at her.
    “Wavey,” she said,