What Stayed Behind

The boot prints went north through the maintenance corridor, away from the relay access point and toward a section of the original colony that the briefing maps had labeled PROCESSING — SECTOR 7, DECOMMISSIONED. The prints were multiple — Mace counted at least three distinct tread patterns, all human, all relatively recent given the absence of settled particulate in the impressions.

He tracked them with the methodical attention he'd learned to give to things that didn't fit. Things that didn't fit in the briefing were either errors in the briefing or surprises in the field, and surprises were the enemy of 72-hour operations more than the Keth were.

Wire had gone ahead. Frost was on Mace's left, Mena and Okafor behind. The corridor was sealed from above by layers of Keth organic coating — they were below the Keth inhabitation level now, in the part of New Carthage that the Keth had never bothered to explore because their occupation of the dome didn't require them to go underground. The maintenance tunnels were cold and dead and silent and recognizably human, which made the silence feel specific rather than empty.

"They're recent," Mena said, studying a print.

"Two weeks, maybe three," Mace said. "Hard to say without a controlled environment."

"They're not military."

He'd noticed that too. The tread patterns were civilian — two different boot styles, one military-adjacent, one closer to work boot. Not standard issue. Not insertion-team gear.

"Contact," Wire said, from the north end of the corridor.

It was not the alert tone. It was the other one — lower, more careful, the one he used when contact didn't mean open fire.

Mace moved up.

Wire was at the end of the maintenance corridor at a junction where the tunnel branched, kneeling, weapon down at forty-five degrees. Beyond him, where the branch widened into what the map indicated had been a secondary environmental control room, there was light. Warm light — not bioluminescent blue-green, not Keth. Incandescent. Battery-powered, the kind of light a human used.

And beyond the light, a face. Two faces. Then a third, appearing at the edge of a partition.

Human faces. Gaunt, guarded, alive.

"Don't shoot," a woman said. She said it in the flat register of someone who had said it before and knew the value of saying it slowly. "We have been here eleven years and we know this tunnel system better than your briefing does. If we wanted to hurt you we would have used the north access when you came through."

Mace lowered his weapon. Not all the way. To the angle that communicated listening rather than threatening.

"How many?" he said.

"Thirty-one." She stepped forward into the light. She was perhaps fifty, with close-cropped gray hair and the particular lean of someone who had spent years in low-calorie conditions. She wore a patchwork of original colony gear and salvaged materials. "We were thirty-seven. We lost six in the first year and haven't lost anyone since, which I am going to attribute to a combination of skill and stubbornness." She looked at the team, moving her assessment from face to face. "You're not a standard patrol. You're SOF."

"Sergeant Mace Alvarado," he said. "Fireteam Ghost. We have a mission objective in the maintenance level below this section."

"The Keth relay," she said.

He didn't confirm it.

"We know about the relay," she said. "We've been living under it for three years. They built it when they reinforced the dome—" She said they with a specificity that was different from how people said it on the ships. More particular. Like a neighbor you disliked rather than an enemy you feared. "My name is Dr. Yael Oris. I was the chief xenobiologist for the New Carthage research station. I stayed because evacuation was not a medical option for seventeen of our people and I wasn't leaving my people." She paused. "Come inside. You need to know what you're walking into."

The secondary environmental control room had been converted into something between a shelter and a command post — cots, a solar-cell power array running off the dome's maintenance conduits, food storage in sealed containers, and on one wall an enormous hand-drawn map that covered the entire surface. The map showed the dome of New Carthage in detail that no briefing Mace had seen had matched. Every Keth movement pattern, every relay node, every access route, every patrol timing. Three years of observation, drawn in pencil on repurposed maintenance paper.

"They changed the patrol timing four days ago," Oris said, standing in front of the map. "The relay deployment changed the same day. Whatever your briefing told you about patrol density and response time is out of date."

"We noticed," Frost said, and then caught himself. "Sorry. Noted."

Oris looked at him without judgment. "The relay access is guarded by six Warforms on a rotating cycle. But the rotation changed with the patrol timing. Currently it's a fourteen-minute cycle instead of twenty, which changes your window for a breach significantly." She pointed to the relay access on the map. "You go in here. Through the organic growth — they've layered it over the original access panel, you'll need tools to get through it. Below that is the relay chamber. The relay is large — your ordnance will need to be substantial."

"It will be," Mena said.

"The critical issue," Oris continued, "is that you have fourteen minutes from breach to detonation. If the Warforms complete their cycle and find the access compromised, you won't have fourteen minutes. You'll have four, and four is not enough to set the charges and get clear." She looked at Mace. "Someone needs to extend the window. Hold the patrol off the cycle long enough for your demolitions operator to work."

The room went quiet.

Wire was looking at the map with the specific focus he brought to geometry problems. He turned to Mace.

"North corridor access," he said. "I can draw two of the six from the relay rotation. Single shooter, confined space, they don't know the tunnel system. I can hold a four-minute window indefinitely with the right position."

"That's not the math," Mace said.

"The math is whatever I decide it is," Wire said. He said it without heat. Factual. "You need a window. I can make a window. I don't need you to agree with me about whether that's optimal. I need you to take the window when I make it."

"Wire—"

"Sergeant." Wire turned to face him fully, which he almost never did. He had gray eyes and an expression that was not reckless and not suicidal and not any of the things that usually accompanied a volunteer for a terrible position. He had the look of a man who had done the calculation and was at peace with the result. "You need me to do this. I know what I'm doing. Let me do what I do."

Oris was watching them. The other survivors in the room were watching. Frost had the expression of someone trying to decide if he was about to watch something happen that he couldn't stop.

Mace looked at Wire for a long moment.

"Four minutes," he said. "We need four minutes at minimum. If the charges aren't set in four minutes, we have a different problem."

"Four minutes," Mena said. "I can work with four."

Wire nodded once. He went to his pack and began prepping for a solo position.

Mace turned back to Oris.

"We'll need someone who knows the relay chamber," he said. "Someone to guide us in."

"I'll go myself," she said. "I've been inside three times. I know where the relay core is and I know what's around it." She paused. "There is also something you need to see when you get there. Something that wasn't in your briefing because your briefing was assembled from sensor data and sensor data doesn't capture context." She looked at him steadily. "The relay is doing something more than jamming your fleet. I don't know exactly what. But I've been watching the Keth for eleven years and I know when they're doing something significant."

Outside, distantly, the sound of Keth movement. Patrol cycle, passing above them, the bioluminescent signal running through the organic coating of the walls.

"How long until Wire needs to be in position?" Mace asked.

"Twenty minutes," Wire said, from across the room. He was already done prepping. He was sitting with his rifle across his knees, same position as the drop pod. "No rush."

Mace looked at his mission clock. Forty-one hours, twelve minutes remaining of the seventy-two. The fleet was blind. Somewhere in the space above Titan, seven hundred ships were deaf and dark and waiting.

He looked at Wire.

"You come back," he said.

Wire said nothing.

He picked up his rifle and went to find his position.