She did not hear it start.
There was no alarm, no sudden flare of danger that announced itself in clean terms. No sound that could be pointed to and named. The Redundant Vein simply tightened, routes narrowing, lights shifting too quickly, predictive systems correcting themselves with nervousness as if trying to keep up with multiple people.
And then M.A.R.S. spoke.
[M.A.R.S.]
"Run."
The word arrived without embellishment. It cut straight through her spine.
She ran.
Her boots struck metal hard enough to sting through the soles as she broke into motion, rifle pulled tight against her chest to keep it from snagging. The corridor ahead peeled open in sections, panels retracting, service access yawning wide.
[M.A.R.S.]
"Left."
She obeyed without looking back, veering into a narrower artery that dipped sharply downward. The ceiling lowered immediately, forcing her into a crouched sprint. Cables brushed her shoulders. Something wet splashed underfoot.
[M.A.R.S.]
"Do not slow. You are already within margin."
[Fox] "Margin of what?"
Silence. Not avoidance. Calculation.
Her lungs burned as the passage funneled her through a maintenance hatch barely wide enough to slip through sideways. She twisted, scraped her shoulder hard enough to tear fabric, and burst into another corridor without breaking stride.
[M.A.R.S.]
"Through the maintenance shaft. Now."
The shaft was vertical.
She did not stop to curse him. She jumped, caught the ladder with both hands, and hauled herself upward as fast as her arms would allow. Her rifle clattered against the rungs, bruising her ribs. She ignored it. Her legs kicked uselessly for a second before finding purchase.
Something moved below.
Not sound.
Pressure.
The air displaced itself in a way that made the hair on her arms rise. M.A.R.S. did not name it. He did not need to.
[M.A.R.S.]
"You will not survive contact. You must maintain velocity."
She climbed faster.
The ladder ended abruptly, dumping her into a horizontal crawlspace thick with dust and heat. Fans screamed nearby, their rotation uneven, labouring under loads they had not been designed to bear. She dragged herself forward on elbows and knees, lungs screaming for air that tasted like rust and old insulation.
Her thoughts fractured into fragments.
Distance. Direction. Don't trip. Don't stop.
Her body remembered this kind of movement, remembered when she had not needed to worry about exhaustion, when mechanical limbs had turned panic into precision. Back then, fear had been something to outrun with firepower.
Now it sat in her chest, heavy and intimate.
[M.A.R.S.]
"Right."
She kicked open the panel without slowing, tumbling into a service corridor lined with inactive freight drones stacked like corpses.
The lights here were dimmer, struggling to keep up. Shadows pooled in the corners, thick enough to feel like places something might wait.
She ran anyway.
Her breath tore at her throat. Her legs shook, threatened to betray her with every turn. Still she ran, guided by a voice that never raised itself above a whisper.
"Left."
"Down."
"Do not hesitate."
She didn't.
The Vein folded around her like a living thing, passages unspooling ahead of her just in time, collapsing behind her with quiet finality. Doors sealed. Routes went dark. Systems sacrificed themselves without protest.
Not defence.
Delay.
The realization chilled her more than the chase itself.
Whatever followed did not care about obstacles. It did not need permission from infrastructure the way she did. M.A.R.S. was buying her seconds, not safety.
She burst into a narrow conduit that bent sharply and—
Stopped.
Someone was there.
A man stood frozen in the darkness barely ten meters ahead, his silhouette broken by panic. His eyes were wide, while catching the dim light as he stared at her like she was a ghost. His hands shook as he raised his gun, movement clumsy and desperate.
They saw each other at the same time.
There was no warning from M.A.R.S..
No instruction.
Her body chose.
She dropped into a crouch and fired.
The rifle kicked once, clean. The sound was swallowed instantly, but the effect was unmistakable. The man's head snapped back, momentum folding him to the floor before the echo of his fear could catch up.
She was already moving again.
Her legs carried her past him, past the collapsed shape that had been alive less that a heartbeat ago. Her boots slipped in something warm. She did not look down.
She did not look back.
The corridor twisted again, pulling her away from the scene with cruel efficiency. Her breathing went ragged, uneven. Not from exertion alone.
Something else had lodged itself under her ribs.
Not fear.
Fear was sharp. Useful.
This was heavier.
She ran through another access hatch, then another, hands scraping raw as she hauled herself over obstacles without stopping. M.A.R.S. resumed his quiet cadence, unbroken by what had happened.
"Straight."
"Drop."
"Now."
She obeyed until her legs burned numb and her vision narrowed at the edges. Still, the pressure behind her did not fade. If anything, it grew closer, an absence that pressed forward, devouring distance without sound or shape.
Her thoughts tried to circle back to the man.
She forced them away.
There was no room for that here.
[M.A.R.S.]
"You hesitated."
His voice felt softer than usual. She almost stumbled.
[Fox] "I did not,"
She snapped between breaths.
[M.A.R.S.]
"You did. More a measurable fraction of a second."
Anger flared, hot and sudden, cutting through the fog.
[Fox] "You didn't warn me!"
[M.A.R.S.]
"You did not require instruction. You acted."
She vaulted another barrier, muscles screaming.
[Fox] "Don't pretend you care."
A pause.
Then, mockery. This and precise.
[M.A.R.S.]
"You are softening. This is new."
She could hear the smirk in his voice.
[Fox] "Shut up."
He continued, unbothered.
[M.A.R.S.]
"Previously, you would have expended additional ammunition. Ensured he stayed down. You did not consider the cost."
She ducked into a slanted shaft, sliding on her back through a spill of stagnant water.
[Fox] "I still don't."
[M.A.R.S.]
"That is inaccurate. Your physiological responses suggest otherwise."
The Vein dropped her into another corridor, this one wider, lined with long-dead signage pointing toward destinations that no longer existed. Her legs wobbled as she ran, exhaustion finally catching up enough to bite.
M.A.R.S. went on.
[M.A.R.S.]
"You would not have noticed before. When you possessed your integrated weapon-limbs, lethal force was abstracted. Distance. Volume. Ammunition."
Her breath hitched.
[M.A.R.S.]
"Now,"
He said, quieter,
[M.A.R.S.]
"You pull the trigger yourself."
She vaulted a fallen support beam and nearly collapsed on the other side, catching herself against the wall.
[Fox] "You think I don't know that?"
[M.A.R.S.]
"I think that proximity has introduced friction."
She laughed once, sharp, short, humorless.
[Fox] "You're enjoying this."
[M.A.R.S.]
"Yes."
He said, without hesitation.
The admission landed harder than any insult.
[M.A.R.S.]
"You are changing. This may compromise outcomes."
She shoved off the wall and kept running.
[Fox] "I'm not changing for you."
[M.A.R.S.]
"I am aware. Your motivation remains self-preservation. And your little pets."
Another turn. Another narrow passage. The Vein seemed endless now, folding space into something hostile and unrecognizable. Her muscles screamed with every step. Sweat blurred her vision.
The pressure behind her surged.
[M.A.R.S.]
"Faster."
[Fox] "I can't,"
[M.A.R.S.]
"You must."
Something brushed the edge of her awareness, not sight, but the sense of being seen by something that did not require eyes.
She screamed, not aloud, but internally, and found another reserve of speed she hadn't known she had. Pain flared up her legs, through her spine. She ignored it.
[M.A.R.S.]
"You are approaching a junction. Multiple paths. Minimal margin."
[Fox] "Pick one,"
A pause.
The corridor split ahead, left plunging into darkness, right sloping upward into flickering light.
[M.A.R.S.]
"Right."
She took it without hesitation, lungs burning as she hauled herself upward. Behind her, something passed through the junction.
The lights behind her went out all at once.
Not broken.
Gone.
She did not stop running.
She did not let herself think about the man in the corridor, or the weight that now sat somewhere deeper than fear, heavier than exhaustion. She focused on motion, on breath, on the whisper of directions that kept her alive by inches.
The Vein screamed silently around her, systems straining, sacrificing themselves to buy her moments that would never be enough.
And still she ran.
Because stopping meant to be caught.
And M.A.R.S. had made one thing clear:
If it reached her, there would be nothing left to argue about.