Hesper Nakagawa (Human, Survey Lead, Fliade survey)

Nakagawa had slept on it, which was the only test the survey had ever trusted, and in the morning it looked the same, which is how you know.

"We knock," said Nakagawa, at the station, before anyone had eaten. "Today. Before the shift, not after. Here is how."

Egede had objections and Nakagawa let Egede have them all, in order, because a rule kept without the objections to it teaches nobody anything, and then answered them in order too.

The rule about the surface, first, since Egede had been going to raise it. Nothing stays on this world that the planet would keep. So the thing set down at the line would be a stone. Not the party's: the planet's. A stone of the upper levels, picked up at the junction and carried down and put on the silt, which was where it had come from and where it belonged, so that when it was left there, nothing would have been left. The planet already kept it. That was the whole point of a stone, and it had taken the party two years and a returned instrument to see that it was what the people below had been telling them the whole time.

Then when. Before. The boulders shifted before the party was anywhere near the margin; that was the thing that made them a knock and not a comment. So the stone went down first, at the start of the shift, before the imager was even out of its case, and the work came after, if there was any work, and if there was not, the party came back up and that was the shift.

Then who.

"One of us," said Nakagawa. "A knock is one person at a door. Three people at a door is something else, and they have a word for it, and we are not going to find out what it is."

"Then me," said Egede.

"Then Aravena," said Nakagawa. "Who fits the squeeze without scraping half the skin off, and who has been asking that question at the bottom of the passage for sixty shifts, into the dark, when the work was done. You didn't know I knew. I knew. It is on the sound channel every night." Aravena had gone a colour, and Nakagawa let that be. "It is the right question. It has been asked from the wrong place. Today it gets asked from the right one, and by the one who asked it."

Then the rest, plainly, the way orders are given when they matter. Light held low. To the line and not one step past it. Set the stone down, on the line, and step back, and wait the interval — the interval the party had measured a hundred times from the other side — and whatever happened in it, or did not, come back through. Nakagawa would write the log.

"And if something is there," said Egede.

"Then something is there," said Nakagawa, "and the log will say so."