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“I’m told it’s the hardest part.”

She works in silence for a stretch, and I leave it be, because the quiet has stopped being a thing either of us needs to fill.

“I keep waiting to feel like I lost something,” she says eventually. “The flat. The class list. September. I built that whole life and I was good at it and this morning I filed it away under a dead man’s name and I keep checking the place where the grief should be, and it’s just not there.”

“It might arrive late.”

“It might.” She knots something off with a small tug. “But I don’t think it will. I think I spent nine years being the dependable one for children who moved on each June, and never got to be the one who stayed. I’d rather stay somewhere hard than be reliable somewhere easy.”

“That is the most Mountmend sentence you have ever produced,” I say, “and you have been here five weeks.”

“Six, nearly. Don’t undercount me.”

She finishes the shoulder some while past four, and lays her head against my uninjured side, out inside a minute in the way of anyone who has run on the wrong fuel for eleven hours.

CHAPTER 29

CLARA

The building is dying, and it's my dead uncle who tells me how to save it, four months after they lifted him from the marsh.

Here is what a partial scope does to a machine that has spent a hundred centuries being asked one kind of question. It doesn't refuse. That's the horror of it. The archive has no concept of a bad-faith request, because the ones who built it never imagined anybody arriving in bad faith, so when Cassian enters an instruction that means publish four chambers and seal the rest, the building tries to obey it while it is already mid-way through publishing everything, and the two orders will not cancel each other. They fight.

Selka has the readout and is white to the lips.

“It's tearing its own index apart,” she says. “The full publish wants every chamber addressable. The partial wants sixteen of them gone. It can't hold both, so it's — Clara, it's overwriting the map of itself. In about forty minutes it won't know where its own records are, and after that the transmission is noise.”

“The deposit's already filed.”

“The deposit is only a summary. What's up here is the whole substance. If the index goes, we lose the primary source — not the fact of it, the substance. Eleven million years, unreadable, still broadcasting, forever.”

Forty minutes to stop a ten-thousand-year-old building from forgetting its own name, armed with three verbs, a scope, and nothing else.

And here's the part I'll never fully manage to explain to anybody who wasn't in that stilt house with me for five weeks.

I know he left an answer.

Not because it's in the journals. It's a matter of who he was. Garrick Marlow built something with no one point that could fail. He spread nine artifacts across eleven sites. He copied the ninth artifact across two hundred phials of tinted water. He keyed the full scope so nobody could ever force a partial one. Somebody that thorough would never abandon the machine without a route back from exactly this, because exactly this is the thing he spent thirty-one years being afraid of.

“Selka. The very first thing I ever decoded. The margin index, the eleven marked pages — what was the value on the last one?”

“I don't⁠—”

“It wasn't a bearing.” I'm already dragging the sheet toward me, the one page I carried down here, and turning it over to the back, which in five weeks I never once turned over, because the front carried the approach and I am, all evidence agrees, someone who quits reading the moment the answer she wanted appears. “There was a value under the last bearing that didn't fit the chain, and I flagged it as a mistake, because everything my uncle ever wrote belonged to the chain, and I'd had that upside down all morning, as I'd had it upside down for the five weeks before.”

On the reverse of the sheet, in my own hand, copied from a journal untouched since Sedge End, sits a value I never understood.

Restore from the earliest copy.

“Oh,” Selka says, reading over my shoulder. “Oh, he did not.”

“He did.”

“Clara, that's a rebuild instruction. That's — if this building holds a master copy of its own index, sealed, from before it ever started running, then you can tell it to discard everything since and rebuild off that.” She's already moving to the console. “It would shed the whole span of its self-modification. Every optimization, every rearrangement it's learned —”

“And it keeps the records.”

“And it keeps them. It rebuilds the map, not the archive. Clara, this is — nothing in my grammar means it. Scope, qualifier, publish. Nothing that means restore.”