The time displacement always came in waves.

  That was the only way Jessica had ever been able to describe it... not a jolt, not a cut, but a slow rolling pressure that moved through the ship from the drive core outward, like sound through water. You felt it first in your chest, then in your hands, and then somewhere deeper and less tangible. Vorrin said the sensation was physiological, a byproduct of the field harmonics interacting with fluid in the inner ear. He had explained this to her twice. It hadn't made it feel less like the universe briefly forgetting she existed.

  She'd gripped the handhold above her bunk and counted the waves. Four. The fourth one always signaled arrival, or near enough. The drive wound down with a sound like a held breath finally released, and the Last Kindness settled into local time the way a boat settled into still water after a wake.

  Their third trip through time with Khamm and Vorrin. She was getting better at it, but she still hated it.

  On the observation feed, the planet's surface scrolled past in rust and amber. She made herself look at it for only a moment before she looked away. Vorrin had flagged it on the first pass ... settlements, barely counting as civilization, gathered buildings into small settlements, and something that might have been irrigation beginning at the river deltas.

  The stirrings of something that would, in the long, unspooling timeline they were threading through, become the civilization that had already begun mining these hills and feeding the extinction event they were here to document.

  She didn't look long. None of them did.

  The thermal anomaly was a hundred and thirty meters below the rust-colored hillside, patient and unchanged and entirely unaware of everything above it. Vorrin had the entry route mapped before they'd finished suiting up.

  The cave seemed to breathe as they entered.

  That was the only way Jessica could describe it. The slow movement of air through the tunnels, cool and mineral-dark, carrying something that wasn't quite a sound and wasn't quite a feeling but registered as both. Like being inside something alive. Like the rock itself had a pulse too slow and too old to measure.

  Vorrin had found the entrance forty minutes ago... a crack in the rust-colored hillside that the surface scans had flagged as a thermal anomaly. Underground water source, he'd said, pulling up the data with the efficiency of someone reading a grocery list. Consistent temperature differential. High probability of habitation.

  He'd been right. He was usually right, which Jessica had stopped finding annoying and started finding exhausting.

  They'd come in on foot, no ATV, suits on passive mode... minimal heat signature, no active scanning that might register as intrusion. Vorrin had been specific about that. We observe. That's all. He'd looked at all three of them when he said it, but Jessica had noticed he looked at Deke a half-second longer than the others.

  Deke hadn't reacted. Just checked his suit seals and followed.

  The cave opened up after the first narrow passage ... opened up in a way that made Jessica's breath catch, because she'd been expecting a cavern and what she got instead was something closer to a cathedral. The ceiling vaulted forty feet overhead, and the walls were not dark.

  They were alive with light.

  *  *  *

  The Umara, as they had agreed to call them, moved through the space like they'd never once considered that darkness was a problem.

  There were eleven of them that Jessica could count... though the light made counting difficult, because the bioluminescence wasn't constant. It shifted. Traveled. A pattern would bloom across one creature's chest, travel up toward the antler-like structures rising from its head, and then, she was almost certain, be answered by something similar from across the cavern. A different pattern. A different arrangement of light.

  She watched two of them near the water's edge. The underground spring emerged from the far wall in a thin ribbon that spread into a shallow pool, dark and perfectly still except where they disturbed it. One reached down and touched the surface. The patterns on its skin slowed, became something elongated and soft. The other watched, its own markings dim, and then produced a single pulse of light... just one, traveling from the tip of its tail up the full length of its body to the ends of the antler structures... and the first one made a sound that wasn't quite a sound, more a vibration that Jessica felt in her back teeth, and touched the water again.

  "Vorrin," she said, very quietly. "Are you seeing this?"

  "I'm scanning it," he said. His voice through the comm was controlled in the way it got when he was working hard to keep it that way.

  "That's communication."

  "It appears to be, yes."

  "That's not near-sentient," Maddie said from Jessica's left. Her voice was hushed in the way people got in churches, or at least the way Jessica remembered people getting in churches from a life that felt like it belonged to someone else now. "That's a language."

  Vorrin didn't answer immediately. Jessica heard the soft processing sound of his scanner. "The distinction between complex signaling behavior and language is ..."

  "Vorrin."

  "... I know what it looks like."

  They stayed still. All three of them pressed into the shadow of the cave entrance, where the rock curved and gave them cover. Deke was slightly ahead of the others, one hand braced against the cave wall, watching with an expression Jessica couldn't read from this angle. He hadn't said anything since they entered. Just watched.

  *  *  *

  The cave art was on the eastern wall, past the water.

  Jessica found it when one of the Umara moved in that direction, and she tracked it ... tracked the light of it, really, the slow blue-green glow that made the cave wall legible. And there it was. Pressed into the rock in a technique she couldn't identify from this distance, something between carving and pigment. Shapes. Repeated shapes.

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  Something that might have been the water source. Something that might have been the antler structures. Something repeated in rows along the base that could have been individuals, or could have been a count of something, or could have been something she didn't have the framework to understand.

  She reached up and touched her helmet display, pulling up the passive imaging capture. Documenting. Maddie was already doing the same thing, she noticed.

  The Umara who'd moved to the eastern wall stood before the markings for a long moment. Its bioluminescence moved in a pattern Jessica was starting to think of as slow... the patterns that seemed to correlate with stillness, with something that might have been contemplation. Then it reached out and touched one of the shapes on the wall. Just touched it. Held its fingers there.

  Jessica's throat felt tight.

  She thought about the survey data. About the rust-colored terrain and the remains underneath, and the fact that the surface fauna existed partly because these creatures had died and fed the ground they were buried in. She thought about Maddie's chronicle ... they died a long time ago and helped grow something else in the process ... and looked at this creature touching its own history on a cave wall and felt something she didn't have a word for.

  "Cause of extinction," she said quietly. "Vorrin. What does the scan say?"

  She heard him pull it up. Heard the pause.

  "Surface development," he said. "Large scale. Mining operation, based on the vibrational signature already present in the rock." Another pause. "Progressive structural compromise of the cave system. Projected critical failure ..." He stopped.

  "How long?" Deke said. First words since they'd entered.

  "Seven days. Give or take twelve hours."

  The cave breathed around them. The Umara moved through their light-language, unaware, the patterns traveling across their skin in something that looked, from here, like conversation. Like ordinary conversation on an ordinary evening.

  Seven days.

  *  *  *

  The rock pilings were near the water source, and it took Jessica twenty minutes of watching before she understood what they were.

  Not random. Not structural. The Umara added to them deliberately... she watched one carry a stone from the far side of the cave with the focused attention of someone completing a task they'd done many times, and place it with an unmistakably intentional precision. The piling was roughly organized by size, with smaller stones toward the top, and the placement seemed to matter. The Umara adjusted its stone twice before settling.

  When it stepped back, its bioluminescence did something Jessica hadn't seen before ... a brief, rapid cascade from tail to antler tips, all at once, like a full-body exhale.

  "Are those..." Maddie started.

  "I don't know," Jessica said.

  "They look like..."

  "I know what they look like."

  Graves, maybe. Or markers. Or something that served a function neither word covered. Something that said this mattered in a language built from light and stone and the slow, patient work of placement.

  Deke hadn't moved from his spot near the cave wall. Jessica glanced at him. He was watching the pilings with an expression she recognized now ... the same one he'd had outside the Snarric habitat. Like he was working something out and hadn't finished yet.

  *  *  *

  One of the creatures wandered off from the main group. They couldn’t be sure if they had been sensed or just a random whim of the creature, but it loped lazily down the passage.

  It had been moving toward the eastern wall again ... toward the cave art ... and the ground near the base of the wall was less stable than the rest, the rock fractured by the same developmental vibrations that were going to bring the whole system down in a week. A hairline fault. The Umara's foot came down on it, and the fracture gave, and a section of rock the size of a large dictionary came loose from the wall and caught its leg.

  The sound it made was ... not a scream. Nothing like a scream. A rapid, frantic pulse of light and a vibration that traveled through the cave floor and into Jessica's boots and up through her body and registered somewhere behind her sternum as distress. Pure and unmistakable distress. The other Umara went still across the cavern, their bioluminescence dimming in unison like lights going out.

  The injured being tried to move and couldn't. The rock had it pinned at the shin.

  Jessica looked at Vorrin. Vorrin's jaw was set, and he was already shaking his head, barely, the smallest motion, and she understood what it meant. She understood his reasoning, and she understood the rules, and she understood the timestream, and she understood all of it.

  She was still looking at him when Deke moved.

  Not running. Just ... moving, the way he moved when his body decided before his brain had finished the meeting.

  Across the cave floor in long, quiet strides, dropping to one knee beside the Umara before anyone had said a word. The creature's light went frantic, alarm cascading up its antler structures in rapid bursts, and Deke didn't flinch. Just got both hands under the rock and lifted.

  It wasn't a small rock. His suit's assist engaged with a soft mechanical sound. The rock moved.

  The Umara scrambled back, leg free, and then went absolutely still. Three feet from Deke. Staring at him... or doing whatever passed for staring among a species with those luminous, focused eyes. Its bioluminescence had gone almost entirely dark, just a faint pulse at its chest. Slow. Uncertain.

  Deke stayed where he was. Didn't reach out. Didn't make any sudden motion. Just stayed on one knee and let the creature look at him for as long as it needed.

  Maddie was already beside him, medical kit open, before Jessica had processed that she was moving. "Leg," she said quietly to Deke.

  "Yeah."

  "Hold still," she said, which was directed at the Umara and was completely absurd and was also exactly right, because something in her tone... calm and certain and kind in the specific way Maddie was kind... seemed to register. The creature's pulse of light at its chest steadied. It didn't move while Maddie worked.

  She splinted it with what she had, which wasn't much but was enough. The Umara watched her hands the entire time, that single chest-pulse steady and slow.

  When she was done it looked at her. Then at Deke. Then it produced a pattern Jessica hadn't seen before ... something that started at the splinted leg and traveled upward slowly, like it was tracing the path of what had just happened, and ended in a brief double-pulse at the antler tips.

  Then it moved away. Rejoined the others. And the cave was quiet again except for the sound of water and the soft collective bioluminescence of the group reassembling around it.

  Vorrin didn't raise his voice. He never raised his voice.

  "We have protocols," he said. "We have them for reasons. Every decision we make in the field ..."

  "I know," Deke said.

  "... has potential consequences we cannot fully model. The rules exist because the alternatives ..."

  "I know, Vorrin."

  "You acted without consultation. Without scanning for ..."

  "It was in pain." Deke's voice was flat. Not defensive. Just stating a fact, the way Vorrin stated facts. "I could hear it. Through my boots. I could feel it in pain." He looked at Vorrin. "So I moved the rock."

  Vorrin held his gaze for a moment, then looked at his scanner. Jessica watched him work through it ... the data, the timeline, the variables. The thing he did when emotion wasn't useful, and information was.

  "No deviation," he said finally. Quieter.

  "What?"

  "The timestream." Vorrin turned the scanner so they could see it, though only he could fully read what it showed. "No measurable deviation from the projected outcome. The extinction event proceeds as modeled. The cave collapsed in seven days ..." He stopped. Set the scanner down. "What you did didn't change anything."

  "Okay," Deke said.

  "That's not the point. The point is that we didn't know that when you acted. You made a decision that could have ..."

  "I know." Deke looked at him. "I know it could have. And I'd do it again."

  The silence stretched. Vorrin looked at Jessica, then at Maddie, as if searching for an ally and finding only people who had watched the same thing he had. He looked back at Deke.

  Something in his expression shifted. Barely. The way it sometimes did.

  "One standard week," he said. "We have a rescue window of just seven days." He picked up his scanner. "I suggest we spend the time learning everything we can."

  He walked back toward the cave entrance. Not storming out. Just moving with purpose, the way he always moved, and Jessica recognized it for what it was ... Vorrin ending a conversation by finding the next problem to solve.

  Maddie touched Deke's arm. He looked at her. She didn't say anything, just looked at him with that expression she had that managed to communicate entire paragraphs without words, and he nodded once, and that was that.

  Jessica looked back at the cave. At the Umara gathered around their water source, the bioluminescence moving between them in patterns she was only beginning to read. At the cave art on the eastern wall. At the stone pilings near the water, already having difficulty considering the Umara simply another group of animals.