The Stair That Ends

The relay gave her the terrace in strips. The Sable stood on its landing pad below the hillside; from the tender's console the stair was only a pale slash in the dusk. Every frame on Nell's console ran 3.4 seconds behind her hand on the stick — buffered local link, codec cycle in and out — and there was nothing to do about it but queue.

"Ash, traverse left eight, hold, down two." She stacked the commands before the first one landed, then sat back and watched the old picture while the new one caught up. The crawler went left eight and drifted another degree and a half on the loose gravel at the terrace edge. She saw it three seconds after she could have prevented it, typed the correction, watched the correction land.

Dermot came on while she was straightening the track. "That's two extra passes. Logging dwell."

"Log it."

"Sunset eighteen twenty-three. Pad lights out nineteen hundred. You've overrun me two dusks running, Farrow. Tonight you get one dusk and one core, and Ash is on the pad before night-cold."

She typed the next stack instead of answering. The drill arm came up cold at the terrace floor and stalled at the shoulder, the bit shivering in its cradle, going nowhere. She cycled it, waited out the return, cycled it again. By the time the arm ran free the light had gone amber on the wall.

Eleven treads, and nothing at the foot of them but gravel. No rubble, no mortar scar, no stone reset in a later hand. Three conditions for a reference case, all of them met from orbit. She had spent the season comparing dressed-stone flights on four worlds; this apparently untouched stair was to be the reference against which the altered ones could be read. What she wanted now was the core, the last line of the file filled, and the season shut. She walked Ash up.

The frames arrived late and she read them late. The wall was lichened grey-green; the risers were lichened in the shade of every nosing; the treads were bare — all eleven, no weed in the joints, no grit that had lasted a season.

She brought the lamp under the first nosing and raked it sideways. The underside was dished and polished, a greasy shine along the hollow, no boot-scuff in it. Second nosing, same. Fifth, same.

Along the flight she found the husks: translucent, helmet-shaped, thumbnail and then fist, set one to a tread and graded small to large up the flight. None above the third tread from the top. None on the top tread at all.

The joints had been repointed, and not with mortar. She set the feeler probe to a seam and it came back tacky, a thin glassy cement that held the shape of the scrape; pressed harder, the probe skated off the seam and took a crumb of the stone beside it. An hour after the sun had left the wall, in shade, the seam still pulled.

The thermal came back with the sixth tread four degrees above its neighbours. She set the lamp down on it, and the next frame showed her a husk, still soft, slumped against the nosing, its rim wet.

She opened her file. Twenty-five millimetres, standard depth, twenty-five minutes of dwell from the moment the bit touched. Start now and it finished at 18:51. Recovery to the pad, seven minutes if the gravel behaved — 18:58. Lights at 19:00.

"Clock's running," Dermot said.

"I know."

"Are you cutting?"

The sixth tread was still climbing. The rim had not dried. The last light was going, and the cut would hold her there with the bit in the stone while the stair went dark. She wrote the four degrees in the log, and the wet rim, and the graded line, and left the meaning of them in a separate field where it belonged.

She looked at the file's title. Reference case. She looked at the tread.

"Ash, hold," she said, and typed it, and had 3.4 seconds to change her mind.

The hold landed at 18:27:09, give or take the relay's 3.4 seconds, and the drill arm stopped where it was, bit still cold, an inch off the top nosing.

"Ash, cradle," Nell said, and typed it.

While the command went out and the acknowledgment came back she watched the arm. It had stalled twice that afternoon on cold joints; now it swung clean, retracted, and seated in the cradle with a click she heard through the console audio. She cowled the lamp to low red. The stair went from a subject to a shape.

Below the flight, in the gravel, she walked Ash back three metres and parked it. The treads stood above the crawler's camera in a line of pale edges. The sixth was still the warm one.

Dermot's voice came flat through the console. "You're holding."

"I'm holding."

"That's your dusk. The core program doesn't run itself."

"I know."

"You've got a window."

"Twenty-five minutes of dwell and the light going," she said. "I can do the arithmetic."

"Then do the core."

She queued a pan and waited for the progress bar to move. "I'm doing something else."

He was quiet a moment. Then: "Logging dwell."

"Log it."

In the low red lamp the pale treads stood clear against the darker risers. At 18:36 the first casque came up the gravel at the stairfoot and started to climb.

It was small, translucent, helmet-shaped. It climbed on six pale legs and stopped on the bottom tread. It hooked the rim of its old shell under the nosing, braced, and shed — the husk dropping free, the new shell soft and wet in the last light. It stood while the stone warmed it. Then it stepped off the edge and the air took it, downwind.

The next came, and the next. One to a tread, small ones low, larger higher, graded as the husks on the flight had been. Each hooked, shed, cured, stepped off. The lacquer on the new shells shone where the low red caught it. When the sixth emptied, the thermal dropped a degree.

"Long lens," Nell said. "Can you put it on the stair?"

"Timecode's already synced," Dermot said. "You want the whole flight?"

"Whole flight. Don't track. Let them cross the frame."

She queued the pan in steps, allowing for the relay before the camera moved. While it waited she queued the next. The tender's long lens gave a second angle, tighter, the same timecode along both feeds. She let the frames accumulate: husk, shed, cure, step, wind.

By 18:44 the last was gone downwind and the treads stood empty, wet in patches. From below, the nosings were dished and polished where the old shells had hooked and dragged. The joints were glossy where the lacquer had run and set.

"Light's going," Dermot said.

"Two samples."

She drove Ash to the stairfoot, where the shed husks lay in the litter, and took one with the small gripper — whole, dry, light as a seed case. At the wall base a detached spall flake lay in the gravel; she lifted it without working the wall. One husk. One flake. She sealed both in the sample box and logged the weights.

In the site file she changed the status from reference candidate to active biological use. In the notes she wrote: casque shedding, curing, dispersal observed at dusk; treads kept clear by traffic; joints repointed by lacquer; no drilled sample taken. She left the builders' field and the open-air ending blank. In the comparison table she moved 41-Kesh out of the reference row and left the cell empty.

"Ash, pad," she said.

The crawler turned on the gravel, drifted left as it always did, corrected, and ran the wall line at its flat gait. The pad lights came up yellow ahead. She counted the last metres against the clock: eight minutes.

At the lock Nell lifted the sample box from Ash's return tray. Dermot met her there. "Eight minutes."

"Eight minutes."

"The Sable lifts at oh-six-hundred for resupply. Kesh isn't on the return itinerary."

"I know."

"Then you know what you just gave up."

She set the sample box on the bench. "I owe you the first hour of the next site's buffer."

He looked at the box, then at her. "First hour," he said. He set the box beneath the bench lamp and pulled up a chair.