Read Chapter 18: Countdown to Impact

The maintenance tunnel smelled of hot copper and sweat. Elias pressed his palm flat against the junction box, feeling the vibration of the Ark's heartbeat through the metal—thrumming, steady, oblivious to the eight hundred people about to die.

"Seventy-two hours," Mara said from behind him. Her voice carried the weight of everything she'd seen in the last day. The Reinhardts. The cavity. The betrayal of a brother who'd sold her out before she ever knew she was worth selling.

Elias didn't turn. "We make it count."

The Level Nine power loop sat behind a hatch that had rusted shut years before the asteroid ever entered the tracking systems. Kruger had given him the route, the codes, the timing windows—and Elias still didn't trust a word of it. But trust was a luxury for people with time.

"Torch," he said.

Petrov handed it over without a word. The Russian's hand trembled. His name was still on the purge list, and every minute they spent inching through these walls was a minute his death warrant stayed active.

The torch flame kissed the rusted bolts. Metal pinged as they cooled. Elias worked methodically, the way he'd worked mountain rescues in his old life—one move at a time, never thinking about the fall below.

"I've got movement," Roth whispered from the tunnel's mouth. The old executive had appointed himself lookout, trading his insider knowledge for a chance to survive his own consortium. "Two guards, Junction Seven."

Elias paused. Kruger had promised the corridor would be clear until 0600.

"Check again."

"I know what I saw."

Elias forced his hands to keep moving. One bolt. Two. If Kruger had betrayed them, they'd never make it back to Mara's cavity, let alone to Level Nine. But if he hadn't, they might still pull this off.

The hatch swung open.

Inside, the power loop hummed—a separate, isolated system that the AI had never been wired to monitor. Three conduits, one control panel, a single override keypad installed by the original builders as a failsafe against their own creation.

Elias stepped in. Reached for the keypad.

"That's it?" Mara asked. "That's the whole rebellion?"

"The algorithm runs on logic. We feed it a contradiction." Elias began inputting the deactivation sequence Roth had given him. "Something that makes its calculations invalid. It'll be forced to re-evaluate the entire purge system."

His fingers moved across the keypad. Three digits in. Five.

The bunker shuddered.

Elias's hands stopped. The floor vibrated beneath them, a low groan traveling through the concrete and steel. The lights in the tunnel flickered once, twice.

Then the hum of the power loop died.

Silence.

Absolute, suffocating silence.

Petrov was the first to understand. He grabbed Elias's shoulder, spun him around, and there was something ancient in his eyes—a knowledge that preceded the technology, preceded the bunker, preceded everything. "The scrubbers," he said. "The oxygen scrubbers."

Elias pushed past him, back into the tunnel. The emergency strips had gone dark. In the pitch black, he could hear the others breathing—quick, panicked, and suddenly precious.

"Roth," he called. "Roth, what happened?"

A pause. Then Roth's voice came from the dark, thin and reedy. "Someone tripped the secondary breaker. The one I told you about. The failsafe."

"I didn't touch the fucking failsafe."

"Someone else did."

The words landed like a punch to the gut. Elias reached out, found Mara's arm in the darkness, squeezed. He could feel the panic rising in the group around him—seven people who'd trusted him to lead them somewhere safe.

"How long?" Petrov asked.

Elias closed his eyes. He knew the math. He'd run it a hundred times during maintenance drills on the upper levels. A closed bunker without scrubbers had maybe four hours of breathable air. Four hours, eight hundred people, and no way to reach the surface.

"Long enough," he said.

Getting back to the maintenance corridor took an eternity in the dark. They moved hand-over-shoulder, a chain of bodies feeling their way through tunnels lit only by Roth's dying flashlight. The hum of the Ark's systems had gone quiet. The whole place felt like a tomb.

Mara found him in the dark, her breath hot against his ear. "The fallback position. Level Eight's ventilation junction."

"The scrubbers are there?"

"No. But the junction has its own isolation valves. We can vent CO2 manually."

Elias kept moving. Manual venting wouldn't save eight hundred people. It wouldn't even save eight. But it might save seven, and right now, seven felt like a number he could still hold on to.

They were three corridors from the junction when Elias felt the change in the air. Thin. Stale. His chest tightened with an animal instinct older than language.

"Seal the doors," he said.

Petrov was already on it, hauling a bulkhead door shut behind them, locking it against the spreading bad air. The group pressed forward, eyes wide in the flashlight's beam.

The ventilation junction was a steel chamber the size of a shipping container, lined with vents and valves and gauges that hadn't been calibrated in a decade. Elias started working immediately, cracking valves, redirecting airflow, trying to coax whatever oxygen remained into the space.

Mara was quiet. That scared him more than the dark.

"Someone did this deliberately," she finally said.

Elias didn't answer. He was thinking about Kruger's too-easy offer. About Visser's twelve-hour deadline that had come and gone. About the fact that the AI had known about the Level Nine loop all along—that it had let them find it.

"Visser," he said.

Roth looked up. "What about him?"

"He built the algorithm. He knew every weakness in the system, every failsafe, every way in." Elias's hands kept moving, working the valves. "He didn't build it to fail. He built it to catch people like us."

The air in the chamber was getting thicker. Harder. One of the group—a woman whose name Elias never learned—sank to her knees.

Mara caught her, checked her pulse. "Elias."

"I know."

"Elias, she can't breathe."

Elias looked at his sister. Then he looked at the vault blueprint folded in his pocket—the one Roth had given him, the hidden vault where Dürr had stashed his stockpile. If they were going to die down here anyway, he could think of worse ways than breaking into the vault of the man who'd sold them all.

"There's another way," he said. "And it's one Visser never accounted for."

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The air grew thin enough that sound itself seemed to fade. Somewhere in the bunker's gut, an AI watched with calculating patience, waiting for its oxygen-scrubber warning to become a scream.