"They’re not expecting ever to see this book, but they think they can maybe raise the avanc anyway. If we give them this-" He waggled it, and the pages flapped like wings. "-maybe it’s all they’ll need. Maybe they’ll just look through these pages, and do whatever decoding they have to do to make sense of it, using you, using all the other translators and scientists in the Lyceum and in the Grand Easterly… Maybe everything they’d need to raise the avanc is right here. We might just be handing them the last piece they need."

He was right. If Aum’s claims were true, all the data he had used, all the information, all the configurations were there in those pages.

"But without this book," Silas continued, "we have nothing. Nothing to sell you to them, nothing to entice them to the island. They’ll just head off as they were planning, and work on whatever they’ve got, and maybe raise the avanc anyway. If they had nothing, they’d make do. But if we give them a part of what they want, they’ll have to have it all. We have to turn this from a gift… into bait."

And after a moment, Bellis understood. She pursed her lips and nodded quickly. "Yes," she said. "Give it to me."

She leafed through to the data appendix and paused, wondering how to start.

Eventually she shrugged and simply tore out a clutch of pages.

After that initial, oddly euphoric moment, she was more careful. She had to make it look right. She thought about other damaged volumes she had seen, picturing the misfortunes that could befall books. Water and fire? Mold? Those were impossible to mimic well.

Trauma, then.

She placed the appendix open, flat, on a strategic nail on her floor, trod on it, and kicked it hard. The nail hooked into the equations and footnotes and yanked them away, to lie in a crumpled pile.

It was perfect. There were three pages at the start of the appendix, where terms were discussed and defined, and then the paper was torn out by its roots. Only the ragged fringes remained, little wedges of half-eradicated words. It looked like the result of a random, stupid accident.

They burned the appendix, whispering like reprobate children.

It did not take long for all the pages to vent as smoke and particles out over Armada, where the wind took and dissipated them.

Tomorrow we make our move, thought Bellis. Tomorrow we start.

The wind was from the south. The fingers of smoke from Armada’s chimneys pointed back the way they had come.

Standing on the deck of the Shadeskinner and looking out, with her back to the city, Bellis could pretend that she was on a normal ship.