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"Yes."

"Okay," she says.

Neither of us returns to it. We finish the survey, we log out, the wall goes dark the instant her hand leaves my arm, and we climb.

There is a word in my language for what happened in front of that wall. It doesn't belong in a work log, or on a colleague, and certainly not on a human who has been on this planet twelve days.

I decline to think it.

I climb four hundred rungs declining to think it, which is its own answer, and I know that too.

CHAPTER 5

CLAIRE

Four days after the relay, I finally have a shape for the missing draw, and the shape is horrible.

The relay leaks. Not power — protocol. Every time it wakes it broadcasts a handshake, the handshake gets answered, and by triangulating the delay across three separate wake cycles I can put a rough volume on whatever is doing the answering. It sits beneath the Founders' tiers, the oldest four districts. It isn't a room, and it isn't a vault. Judging by the return spread it runs somewhere between nine and fourteen square kilometers, starting about sixty meters below the level the city insists is bedrock.

"That's a district," Tomas says, when I post it on the wall for him.

"That's two."

"Under a district."

"Under four."

He sits down slowly on an equipment crate. "I've been going underground my whole life and I've been walking on a lid."

We descend on day sixteen to close the triangulation, because three data points and a straight face is not a survey, it's a rumor. Darius takes us in through a service run below the Cistern that he swears is stable, Tomas shores what he doesn't trust, and the four of us get eight hundred meters along a horizontal bore before the walls open up.

They come out of recesses I didn't see because there was nothing to see. Three of them, hanging at shoulder height, matte and dull and roughly the size of a large dog, each carrying a folded arm along its underside that unfolds into something with a working edge.

"Back," Darius says. Not loud.

We back. They advance in formation, and the formation is what saves us, because it's wrong.

Security sweeps a room. These things are sweeping a floor.

"They're overlapping," I say. "Look at the pattern — fifteen percent overlap on every track. That's not a search. That's coverage. That's how you clean something."

"Claire."

"They're maintenance units."

"They are cutting the wall."

They are. The lead unit drags its edge along the bore lining as it comes, opening a bright line in the ferrocrete, and it's doing that because we are in its way and it was told, during a war six hundred years ago, that things in its way are debris.

Which means the security behavior is on top. Bolted on. Anything bolted on can be outranked.

"Tomas, get your tech out. Darius, I need ninety seconds."

"You don't have ninety seconds."

"Then I need them anyway."

I go down on one knee with the reader and my hands aren't steady, and I make them steady, because the handshake capture is four days old and I have never once flashed a protocol emulator against a deadline like this.