Hesper Nakagawa (Human, Survey Lead, Fliade survey)

Nakagawa read the channels every evening at the station, after the others had eaten, because a thing read the same day is a thing you can still do something about. Sound channel, nothing. Thermal, nothing after the party left. Imager.

Nakagawa ran the imager's playback twice, and then sat for a while, and then went and got the other two.

"Look at that," said Nakagawa, and pointed.

At the mouth of the third passage, at the edge of what the working light had reached before the party took it away, in the fungus-dark the imager could just work by: a shape. Dark. Upright. About the size of a person. Still. It had an edge. That was what Nakagawa had sat with: not that it was dark, since the dark was dark, but that it had an edge, and the edge was lit, thinly, all the way round, the way a thing is lit when the light goes round it instead of onto it. It had arrived between one frame and the next, and stood for forty seconds, and was not there.

"Thermal," said Egede.

"Nothing."

"Sound."

"Nothing."

"Mass."

"Nothing. Nothing on any channel but the one you are looking at."

Egede looked at it for a long time, and Nakagawa watched Egede look, and saw the moment the explanation arrived, because it arrived the way Egede's explanations did, all at once and with relief in it.

"That's a dead region," Egede said. "That's the imager. A sensor block dropping out. It reads dark because it's not reading. You get a hard edge because the block has a hard edge. It's not a return, it's an absence of return."

"The thermal channel also has an absence of return there."

"The thermal channel is a different instrument. A warm thing in that spot would show. Nothing shows. So nothing's there, and the imager has a fault. I'll recalibrate in the morning."

It was a good explanation. Nakagawa had been doing this long enough to know that the trouble with a good explanation is that you stop looking at the thing it explains. "Log the fault," Nakagawa said. "And log the shape. Both. Where it was and how long, and the edge."

"The edge is the block boundary."

"Then it will be the block boundary in the log, and when you've recalibrated, we'll see."

Aravena had said nothing. Aravena was still looking at the screen, at the place where the shape had been, after it was gone, and Nakagawa noticed that, and put it aside.