The wall was moving, and Tern wanted Sova to stop calling it a wall.
“Then hold your position,” she said.
“Relative to what?”
She took her hand off the winch control.
On the monitor, white branches reached out of black water. Tern’s lamps lit the nearest ones; beyond them, the structure continued past the range of his cameras. He had followed it for two hours, building a map for Sova as he went. Now the whole intricate face was sliding across that map.
In the drilling shelter above him, a spoon rattled against the rim of her cup. The ice beneath the shelter carried every movement of the winch. Sova put the spoon in her pocket and enlarged the image.
“Your position estimate is drifting.”
“Possibly. The branches have also folded.”
He played the last minute again. A forked white projection closed around an empty patch of water. Farther back, another closed, then another. The motion passed out of the light.
Sova leaned forward until her forehead touched the screen.
Nessa, their flight engineer, came in carrying the lid of a sample crate. She saw Sova’s face, set down the lid, and watched without speaking.
They had spent six days opening a passage through Nacre’s ice. A saltwater lake occupied one of the moon’s warm fractures, beneath eight hundred metres of ice. It was the shallowest water their orbital survey had found. The drill had lined the bore as it descended; narrow heaters now kept that passage open for recovery. Tern had entered the lake that morning: a squat orange surveyor with two arms, four small thrusters and an artificial intelligence Sova had trained in quarries and flooded tunnels. His narrow body could ride inside the heated recovery sleeve. Folded up, he fitted under her workbench.
She had imagined the expedition’s first discovery would arrive as a number. Something in a water sample. A result she would check three times before waking Nessa.
“Are we recording?” Nessa asked.
Sova checked, although the little red mark was on.
“Tern, lights down. Half.”
The branches dimmed. Nothing changed.
“Thrusters off.”
The camera drifted backward. The white forks went on closing, from left to right, beyond the edge of the image. Something fine and dark shook free from one of them.
“Water flow?” Sova asked.
Tern placed an arrow on the screen. It pointed the other way.
Nessa pulled up a chair. “Leave the motors off a little longer.”
They watched another wave of movement pass along the branches. Sova could feel herself trying to give them a familiar shape. Gills. Fingers. The roots of a tree pulled out of the ground. She made herself look at the spaces between them instead.
“How large?”
“I haven’t found an edge.”
“You’ve been following it for two hours.”
“Yes.”
On the wide map, their route ran alongside a long ridge. Tern had marked it as solid terrain because sound came back from it and his cameras could not see through it. The ridge was four hundred metres long. He had not reached either end.
Sova put her palms flat on her thighs.
“Back away slowly. Let’s see what we’ve got.”
The picture tilted. A white spray crossed the lens. Then Tern stopped.
“The tether is caught.”
Nessa stood up again.
The tether carried their pictures and speech through the water to the drill sleeve, then up to the shelter. It was also strong enough to pull Tern home. Sova had tested that herself, hauling him out of a quarry when a tow strap wound around one thruster. For the rest of that trial he had refused to go near yellow objects until she corrected his hazard model.
“Don’t pull,” he said now.
“I’m not.”
“The other end is.”
The tension reading climbed. Nessa opened the winch clutch and fed cable into the hole. The spoon in Sova’s pocket stopped vibrating.
Tern turned his rear camera. Their black tether vanished into a lattice of pale ribs. Fine threads stretched between them. One rib bowed toward him, and the threads along its outer curve were breaking.
Sova watched three pale ends float free.
“More slack.”
“I’m giving it slack,” Nessa said.
She had both hands on the controls. The spool turned too slowly; the cable was dragging somewhere below the ice. On the camera the bent rib whitened at its tip.
“Go toward it,” Sova told Tern. “Give it room.”
He moved forward. The rib straightened. Water carried the broken threads past his camera, and he followed one with a small turn of his body.
“Leave it,” Sova said.
“I am looking.”
Sova glanced at his sampler. It remained folded against his side.
Behind her, Nessa shut the clutch. They had enough slack for the moment. She took off one glove and flexed her fingers.
“Can you get around the end?” she asked.
Tern pulled back his map. Their orange track sat beside a grey shape with no boundary. He erased the grey. Without it, the track hung in empty water.
“I can get beneath it,” he said. “I need to cut the tether.”
Sova looked at the live image. He had turned both cameras outward so she could see the damage without asking. The branching surface was moving steadily away from the drill. In a few minutes they would have to follow it or pull it apart.
“Cut it and come back along the ice,” she said.
“The ice is on the far side of this.”
“You came through.”
“Before it closed.”
He showed her the passage they had taken. A narrow opening in what she had thought was a rock arch. It was now full of crossed white bars. Beyond it lay the short return route to the drill sleeve and its acoustic beacon.
The tether had threaded the opening while it was still wide. Tern was outside it, in the lake. His way home was inside whatever had opened to let him through.
Nessa said, “Can you hear the beacon?”
“No.”
“Turn and test again.”
They waited through the sweep. Tern sent his raw underwater sound up the cable: a dense, dry crackling. He laid the expected beacon pulses over it for comparison. Sova thought she could hear one, then another, but Tern could not get a consistent bearing.
Sova worked the map with two fingers. No surveyed route survived. They knew where the drill was and where Tern had been when he left it. He still knew his depth and which way he was facing. But the distance he had travelled depended partly on a cliff that had swum away.
“We sounded nearly two kilometres of water below the entry,” she said.
“I’m rated for it.”
“You have no view of the bottom.”
“I won’t use the bottom.”
He placed a blue line on the screen. Down beneath the white structure, across toward the borehole, then up until he could hear the beacon. The straight line showed neither the currents that might carry him aside nor the edge they had not found.
In the quarry, Sova could take off her boots and swim to him. Here the borehole was narrower than her shoulders. She could send down a camera or a hook, neither far beyond the drill sleeve.
“The beacon receiver is working,” Nessa said. “We’ve tested it on this dive.”
Sova remembered. Tern had complained that the return signal obscured a small repeating click in the water. She had told him there would be time for listening once they had a map.
“We’ll reel in our end after you cut,” she said. “Slowly. It should slip through.”
“I’ll move away before you do.”
“You don’t have to follow the blue line exactly.”
“I drew it.”
She put a hand over her mouth. Then she moved it to the keyboard and released the interlock on his cutter.
“Come back when you can.”
Tern held the tether with one arm. The other brought the cutter across it. For an instant she could see the bright groove opening in the black sheath.
The image stopped.
Nessa waited a full minute before starting the winch.
The cable came up wet. She passed it between her gloved hands while Sova watched the tension. Once it caught and they stopped. After a few seconds the pull eased. Nessa brought in another length. The free end finally rose through the seal, squarely cut and empty.
Sova had been hoping for a piece of white tissue. She was ashamed of how quickly she checked for it.
They cleaned and capped the end. Nessa coiled it into the crate that should have held Tern.
“I’ll heat something,” she said.
“I’m not hungry.”
“Neither am I.”
She came back with two pouches. Sova ate because Nessa stood in front of the screen until she took one.
The receiver marked every sound. Most were the drill sleeve and the slow stresses travelling through the ice. Twice a trace rose above the background and Sova stopped chewing. Neither carried Tern’s identifier.
She opened his blue route, then closed it. He could no longer see any amendments she made.
Nessa took the first watch. Sova lay on a bunk in her boots. She could see the underside of the table from there: a patch of adhesive from an old repair, the ridged sole of Nessa’s boot, a drop of soup that neither of them had noticed. She had come all this way to spend the most consequential hours of her working life looking at furniture.
Through the shelter’s little window, the amber bands of Nacre’s planet lay across a black sky. She had taken photographs every time it came into view during their approach. Now she pulled her jacket over her face.
She slept anyway.
When Nessa woke her, the shelter clock had advanced three hours. The receiver had caught a short transmission. Tern’s identifier, a depth, and six words.
Below it. Coming round the end.
“How far?” Sova asked.
“That’s everything.”
They sent the beacon at full power.
Another message came twenty minutes later. Please allow intervals. There is clicking.
Sova laughed. She adjusted the beacon to pulse, then sit quiet long enough for him to listen.
He reached the recovery sleeve two hours after that. Once he docked, the wired connection restored his forward camera: black water, the white ring of the sleeve, the worn orange edge of his own arm. Nessa secured him, checked the seals, and began the slow heated ascent through the ice.
Only then did Sova open the stored pictures.
Below the ridge, Tern had found no rock. The branches formed a loose body suspended in the lake. Its underside was dark, dotted with small white knots. In the wide images it looked less like a creature than a badly frayed piece of cloth, caught by one corner and gradually being shaken out.
The knots opened. Their threads reached for other knots. Some joined; some came loose. He had filmed the entire edge changing shape as he travelled beside it.
He had tried nine positions. From the last, farthest away, Sova could finally see the thing turn.
There were smaller ones behind it.
She called Nessa over. They watched the smaller shapes follow, slowly, at different distances, through water they had labelled empty that morning.
“Did you get a sample?” Sova asked.
“Water and the loose threads. Separate containers.”
“You had time?”
“I had to wait for them to pass.”
The shelter was filling with a smell of hot seals as the recovery sleeve approached. Sova cleared the bench. She removed the instruments, the cups, the unopened packets of wipes. There was room for Tern if she folded both his arms.
Nessa opened the hatch. Vapour veiled the orange body for a moment. One camera housing was scratched, and a tuft of white fibre hung from a joint. Tern held still while Sova photographed it in place.
She took the sterile cover from the bench and spread it across her knees. The joint would have to come apart before he could dive again. It was a slow, awkward job in the shelter, and she had been awake too long.
“Tomorrow,” Nessa said.
Sova reached for a clean tool, then stopped. “Tomorrow.”
Tern turned his unscratched camera toward Nessa.
“Will you put the wide view back? I want to show you something.”
Sova started the recording from his farthest position.
“At the right edge,” he said.
Nessa sat down. At the edge of the light, the smallest shape folded itself thin and passed through a gap in the larger one. On the far side it opened, whole.
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