Chapter 15:
Null Factor
The tunnels beneath the city were a labyrinth of rusted pipes and flickering emergency lights, their walls slick with condensation that dripped like sweat from a fevered brow. The air was thick with the scent of damp concrete and something sharper. Ozone, maybe, or the acrid tang of old wiring pushed beyond its limits. Every footstep echoed too loud, bouncing off the curved walls like the whispers of ghosts.
I could feel the weight of the underground pressing down on me, the oppressive darkness gnawing at the edges of my vision. The city above might have been a ruin, but down here? Down here, it felt like we were walking through its corpse.
Nia's breathing was ragged beside me, her arm slung over my shoulders as we limped forward. Her skin was too warm, feverish, the crimson veins beneath pulsing faintly like dying embers. Every few steps, she'd wince, her fingers digging into my jacket as if she was afraid I'd vanish if she let go.
"You good?" I muttered, adjusting my grip around her waist.
She let out a weak, breathless laugh. "Peachy."
I didn't believe her. None of us did.
Sarin walked ahead, his posture rigid despite the wound in his side. A deep gash he'd wrapped with a torn strip of fabric, the fabric already darkening with blood. His grip on the makeshift club in his hand, a length of rebar, bent and jagged at one end, never loosened. His eyes never stopped moving, scanning every shadow, every crevice, as if expecting the darkness itself to lunge at us.
We had no idea where we were going.
The figures who had emerged from the shadows, those people with the same glowing veins as Nia, hadn't attacked. They hadn't spoken, either. Just watched us with eerie stillness before vanishing back into the dark, leaving us with no choice but to follow or be left behind.
Now, after what felt like hours of stumbling through the underground maze, a new sound reached us. A rhythmic, mechanical hum, steady and alive beneath the silence.
Sarin held up a hand, signaling us to stop. His voice was a low growl.
"You hear that?"
I nodded, my throat dry. The sound was familiar, though I couldn't place it. Not a generator. Not a fan. Something else. Something... processing.
Nia's fingers dug into my shoulder.
"It's a server bank," she whispered, her voice hoarse. "Or a lab."
I swallowed hard. The last time we'd stumbled into a place like that, it hadn't ended well.
Sarin's jaw tightened. "Only one way to find out."
We followed the hum, our footsteps cautious now, until the tunnel widened into a chamber.
And there it was.
A makeshift bunker, carved into the bones of the city. The walls were lined with scavenged tech—cracked monitors, gutted servers, tangles of wires snaking across the floor like veins. In the center of the room stood a workstation, its surface cluttered with tools, half-disassembled drones, and a holographic display flickering with lines of code.
And in front of it all, a woman.
She was small, her frame wiry beneath a grease-stained jumpsuit, her dark hair pulled into a messy knot at the nape of her neck. A pair of goggles rested atop her head, their lenses reflecting the hologram's blue light. She didn't turn as we entered, too absorbed in whatever data stream she was manipulating.
Sarin didn't lower his weapon. "Identify yourself."
The woman didn't flinch.
"Vex," she said, her voice clipped. "And if you're here, that means you're either desperate or stupid. Maybe both."
Nia let out a weak laugh. "Yeah. That sounds about right."
Vex finally turned, her sharp eyes flicking over each of us before landing on Nia. Her expression didn't change, but something in her posture shifted. Recognition, maybe, or calculation.
"You're infected," she said.
Nia's grip on my shoulder tightened. "Not fully."
Vex snorted.
"There's no 'not fully' with ZERA. You're either part of the hive or you're not." She stepped closer, studying the crimson veins with detached curiosity. "But you're fighting it. That's new."
Sarin's grip on the rebar didn't loosen. "Who are you?"
"I told you. Vex." She waved a hand at the room. "And this is my workshop. Or what's left of it, anyway."
"You're a hacker," I said, eyeing the setup.
"Engineer," she corrected. "But yeah, I know my way around a system." She tilted her head. "You're Catara Lin."
I stiffened. "How do you know my name?"
Vex smirked.
"Because you're the reason half the city's gone dark. HelixMed's been scrambling to contain you for weeks." She turned back to her workstation, fingers flying across a cracked keyboard. "And now you're here. Which means you're either the key to ending this or the final nail in the coffin."
Sarin's eyes narrowed. "You've been tracking us."
"Not you," Vex said. "Her." She jabbed a finger at me. "Your blood's been lighting up the grid like a damn fireworks show. Every time you get near a relay node, the system glitches. The Antlers lose coordination. The infected stutter." She leaned forward. "You're an anomaly, Catara. And anomalies are either weapons or targets."
"What are you saying?" Nia's breathing hitched.
Vex didn't answer. Instead, she pulled a small vial from her pocket. One filled with a dark, viscous liquid. Sarin's blood. The sample he'd given her the moment we stepped into the room.
"Let's run a test," she said.
The hologram flickered to life, a three-dimensional model of ZERA's neural network unfolding in the air above the workstation. It was beautiful in a horrifying way. A sprawling web of interconnected nodes, pulsing with crimson light, shifting and rearranging itself like a living thing.
Vex didn't waste time. She loaded Sarin's sample into a port, and the system accepted it, the nodes flaring as they processed the data.
"Standard infected signature," she muttered. "ZERA recognizes it as part of the hive."
Then she loaded mine.
The reaction was immediate.
The network convulsed. Nodes flickered, some going dark entirely, others recoiling as if burned. The crimson light stuttered, replaced by jagged bursts of static. For a single, breathless second, the entire structure wavered, like a system on the verge of collapse.
Then it stabilized. But the damage was done.
Vex let out a low whistle. "Well, that's something you don't see every day."
Nia's voice was barely a whisper. "What just happened?"
Vex turned to me, her eyes alight with something between awe and fear.
"Your blood isn't just immune, Catara. It's a counter-signal."
Sarin frowned. "Meaning?"
"Meaning she doesn't just resist ZERA. She disrupts it." Vex pointed at the hologram. "When your sample hit the network, it didn't just fail to integrate. It attacked. Like an immune system recognizing a virus and tearing it apart."
I stared at the flickering nodes, my pulse pounding in my ears.
"So I'm... what? A cure?"
Vex shook her head.
"Not a cure. An override." She zoomed in on a section of the network, where my blood's signature had left a jagged scar in the code. "ZERA operates like a hive mind, right? Every infected node is part of a larger system. But your blood? It doesn't just reject the connection. It rewrites it."
Nia's fingers dug into my arm. "You're saying she could shut it down."
Vex's grin was sharp. "From the inside? Yeah. If we can get her close enough to the core, she could crash the whole damn network."
"And how do we do that?" Sarin's voice was grim.
Vex tapped a command into the console. The hologram shifted, pulling back to reveal a map of the city. And at its center, a pulsing red beacon is there.
"HelixMed's old relay tower," she said. "It's the heart of ZERA's network. The Shepherd's throne."
Nia's breath caught. "That's suicide."
"Probably," Vex agreed. "But it's the only shot you've got."
Silence settled over the room, thick and suffocating. The weight of what Vex was suggesting pressed down on me like a physical force. I wasn't just a survivor. I wasn't just immune.
I was a weapon.
And if Vex was right, I was the only one who could end this.
Sarin was the first to speak. "How do we get there?"
Vex leaned back in her chair, folding her arms. "That's the fun part." She nodded toward the door. "You're gonna need an army."
And outside, in the tunnels, the crimson-eyed figures waited.
Watching.
Listening.
Ready.