"That’s the thing," he said. He spoke with care. "It’s in you like your blood." He patted his sternum. "And when it goes bad, when it goes septic, you might say, you bleed it out and then either something else fills it, or it leaves you empty. Sulion ain’t got nothing in him anymore. He wants to grass, and for form’s sake, he’s asking a lot of money for it, but it ain’t the money he wants. He wants to betray because he wants to betray. He wants us to help him go bad. Whether he knows it or not."

They were not in Badside. Here are keys for you, the note had said, pinned by one of the two-horned cesti to the wall. We have a new meeting house. An address. Ori had read the note with Enoch, and they had stared at each other. Enoch was a stupid man, but this time Ori shared his confusion. "Flag Hill?"

At the edge of the city, at the end of the Head Line unrolling north from Perdido Street Station, Flag Hill was where the bankers and industrialists lived, the officials, the wealthiest artists. It was a landscape of wide-open ways and sumptuous houses sheer onto the streets, backing onto shared gardens. There were flowering trees and banyans spilling their knotting creepers and making them roots and trunks, emerging from between black paving.

There had been a slum in Flag Hill for years, like an abscess: an oddity of city planning. Mayor Tremulo the Reformer, two centuries past, had ordered some streets of modest housing built on the slopes of the rise that gave the area its name, so that the heroes of the Pirate Wars, he said, could live by those they had defended. The Flag Hill rich had not welcomed the newcomers, and Mayor Tremulo’s schemes for "social merging" had been made risible. Without money what had been modest became a slum. Slate and brick went sickly. The little community of Flag Hill poor came in and out by train, while their neighbours disdained the raised rails for private hansoms, and waited for squalor to reach a critical mass. It had done so fifteen years before.

The poor had been removed from their collapsing houses, settled in ten- and fifteen-floor blocks of concrete in Echomire and Aspic. And then their once-neighbours had moved curiously into the deserted, hollowed rookeries, and money had at last come. Some buildings had been made into houses for the new wealthy, shored up and two or three holed together: to live in reconfigured "base cottages" became a fashion. But several streets at the heart of Flag Hill’s nameless poverty district had been preserved, architecture as aspic, and made a slum museum.