To the south, though, the explosive-crammed pod rushed over spivvy streets, directly above a barricade at the borders of Aspic and Barrackham. Militia and Collectivist looked up from either side of the wedge of rubble and brick.

The pod overshot open scrubland, sinking as the skyrail angled down, as the estate towers rose toward it. It rushed into the Barrackham Tower.

A one-two-three of explosions as dirty fire blared from the top of the militia spire. Its concrete bulged and split; it was eaten from inside by an unfolding plume; it went up, blew out and began to fall, and the stories below it subsided. In burning slabs like pyroclastic flow the top of the tower slewed off, militia pods falling out and tumbling.

The skyrail went murderously slack, whiplashed down across two miles of city. It coiled through slates, gouging a threadline fault and killing as it came. It dangled from the Flyside Tower and curved toward Aspic, where its hot weight tore buildings.

A spectacular kind of triumph, but one the Collectivists knew would not change the tide.

Most of the workshops by Rust Bridge were quiet, their staff and owners keeping out of sight or protecting the Collective’s borders. But there were still some small factories doing what work they could, for what payment they could get, and it was to one of these that Cutter went on the day the militia tower fell.

The fires of the ancient street of glassworkers were cold, but with a scraped-together purse and political exhortations, he persuaded the seditionist workforce of the Ramuno Hotworks to restart their furnaces, bring out the potash, ferns, the limestone to scour and clear. Cutter gave them the housing with Judah’s circular mirror that he had broken. At last they said they would build him a crystal-glass speculum. He went to Ori’s rooms, to wait for him and Judah.

If Cutter had met Ori before, which was possible given the tight world of the pre-Collective seditionists, he did not remember it. Madeleina di Farja had described Ori, and Cutter had envisaged an angry, frantic, pugnacious boy eager to fight, excoriating his comrades for supposed quiescence. Ori had been something very else.

He was broken. In some way Cutter did not quite understand, but for which he felt empathy. Ori had shut down, and Cutter and Judah and Madeleina had to start him up again.

"It’s getting close," Qurabin said. "It’s getting near, we have to hurry."

The monk spoke more and more urgently: the mind behind the words seemed to degrade a little every day. There had been so many enquiries of that hidden Tesh Moment, more and more of Qurabin must have become hidden.