Harbour was cooling.

The vent’s steady hum had weakened to a trembling sigh. When I pressed my cheek to the stone, the warmth under it faltered, strong for a few heartbeats, then thin again. The water in the hollow had lost its glow. Even the spark-plankton drifted slower, their faint lights paling with each pulse.

I could feel the life bleeding out of this place.

Sleep came fitful, and with it, the dream again.

Not the dark. Not the pressure.

Air.

Heat across skin instead of scales. The scent of tar, salt, and sunlight. Rope slapping mast. A gull’s cry. The horizon rising and falling with the calm of breath.

For a moment, I was weightless. Wind in my hair. The deck beneath my feet shifting with the tide. I inhaled, and air filled me clean and light.

Then I woke.

The warmth was gone.

Cold clawed through my ribs. My gills pulled heavy water that burned instead of soothed. The old ache in my tail returned.

I pressed myself to the stone again, desperate to feel even a trace of heat. It gave none.

The vents were dying.

If Harbour’s warmth vanished completely, I would follow it. The choice wasn’t logic, it was instinct.

I rose from the hollow, slow and stiff, and drifted toward the entrance. The water outside was dim, the vents around the shelf no longer bright enough to paint the rock. The plankton shimmered weakly, falling like faint snow.

A thread of warmer current brushed my flank. Barely there, but enough to notice. It trailed east, toward a deeper slope.

That was all I needed.

I followed.

The water thickened as I descended. Each breath felt like work. My wounds throbbed in rhythm with my pulse. Still, I kept to the thread of warmth, the only trace of life in a sea turning still.

The current wound through a field of low chimneys. Most were dead. A few coughed thin bubbles, their breaths weak and irregular. The heat from them licked my side, quick, fleeting, gone before it could settle.

The plankton gathered around the faint plumes, shimmering in swirls. They looked like constellations scattered over black stone. I slowed to watch, the lights turning and fading with the same rhythm as the dream’s sky.

I clicked softly, mapping the space. The echoes came back warped by heat currents, painting the ridges of stone and the hollow spaces beneath them. My sonar lag was still there, but manageable.

The next vent ahead glowed faintly orange. It wasn’t much, but it was alive. I approached, hovering above it as its breath rose and wrapped around me. The warmth soaked into my scales. The ache eased. My mind sharpened.

My gills fluttered wide, greedily pulling the heat in. The sonar returned clearer. Even the afterimages that haunted my vision from the luminous fry dimmed for a moment.

Then the vent coughed.

The warmth cut off in an instant. The plankton scattered. A tremor ran through the stone.

I flinched back as the vent went still. The orange glow died to grey.

The silence afterward was colder than before.

A new current brushed my tail, hotter, sharper. I turned toward it instinctively, but it burned the edge of my fin as it passed. Reflex pulled me away. Too close to the vent’s throat; the gas there would cook me if I lingered.

I drifted back until the pain dulled. The heat had teeth now. The sea had decided I’d grown comfortable.

I stayed motionless, waiting for the sting to fade. The plankton settled again, circling slowly around me.

When I opened my gills, the faint thermal line was still there, running deeper into the ridge. A pulse of warmth, thinner and steadier. Safer.

Stolen novel; please report.

I followed it.

The path tightened. The rock walls drew close, a narrow fissure barely wide enough for my body. I scraped my scales against the stone as I pushed through. Sparks of pain danced along my sides, reopening half-healed scars.

The sound of stone against plate filled the corridor, low, grating, almost metallic. I slowed, breathing carefully.

Something moved ahead.

A flicker in the current. A shadow gliding across the warmth.

Predator.

Its shape blurred in my sonar, but the pulse of its movement was heavy, slow tail beats, deliberate. Bigger than me.

I pressed myself against the fissure wall, every muscle tight. The shadow passed across the entrance, stirring the water as it went. I felt the pull of its wake tug at my fins. Then, silence again.

I didn’t move until the current calmed.

The warmth beyond flickered, like light glimpsed through smoke. I crawled forward, scraping the last stretch of rock before sliding out into open water.

The corridor gave way to a small basin, ringed by low vents that glowed faintly blue. The heat here was thin but steady, the kind that lingered without shifting.

I let the current lift me upward until the ache in my tail eased again. My body relaxed. The water was breathable, warm enough to keep the cold from crawling back in.

The warmth carried something else too, memory.

Not in words or images, just in sensation. The same rhythm I’d felt above the waves: sun through skin, the sound of waves folding over themselves.

For a moment, I floated in that illusion.

Then the water trembled.

The vent below let out a sudden surge of heat. Not dangerous, but warning. The pulse spread through the basin, shaking plankton loose from the rock.

I drifted higher, watching the heat spread in slow ripples.

This warmth wasn’t constant. It pulsed. A pattern.

The world had turned itself into heartbeat again.

I felt my own match it.

The vents coughed once more, the warmth thinning as quickly as it came. The pattern was dying, unstable. Even this new basin would fade soon.

I couldn’t stay here.

Movement above caught my eye, a faint swirl of plankton rising through a gap in the stone ceiling. A vent current, weaker but rising rather than falling.

I turned toward it.

The drift was gentle at first, almost lazy. It wound upward and east, through a tunnel that shimmered faintly with mineral light. The air, or water, here felt alive again.

I followed, pushing through the opening.

The heat brushed along my sides as I rose. The current’s rhythm steadied, a slow exhale from something vast beneath me.

It reminded me of the surface wind, the way it filled sails. I closed my eyes for half a breath and pretended the current was air again.

When I opened them, the water around me glowed with plankton. Dense this time, filling the tunnel in strands of light that twisted and merged. They moved like rivers of stars, coiling in slow spirals.

I had seen this before, in the night sky of the dream. The same sweep of light, the same quiet motion.

But now it wasn’t dream or memory. It was real, and it was leading somewhere.

The current curved right, tighter now. My body strained to keep pace. The walls vibrated faintly with the pulse of heat pushing through. I could feel the vents below feeding this one, drawing energy from deep in the crust.

The temperature climbed. My gills fluttered too fast. The heat was becoming dangerous again. I slowed, testing each length of water before pushing forward.

A single wrong stroke could boil me alive.

At one point, the current split, one line hot enough to scald, the other barely warm. I veered to the cooler side. The warmth there was thin but safe.

It was enough.

The tunnel widened suddenly, opening into a chamber of dark stone. The walls shimmered with a dull mineral sheen, reflecting the faint light of the plankton drifting between vents.

I hovered in the centre, feeling the warmth swirl around me. It pulsed in cycles, rise, fall, rise, fall.

The sea’s breath.

I tilted my head back, eyes half closed, and let the warmth press against my chest.

For a brief moment, I forgot the cold. I forgot the weight.

The warmth sank deep, reaching the bones that still remembered sunlight. My thoughts cleared again, sharper, cleaner. The afterimages behind my eyes faded to faint ghosts.

I could think. I could feel.

But the warmth wasn’t constant. Even here, the pattern shifted. The vent currents were unstable. The heat that fed me could vanish at any moment, just like in Harbour.

I knew what I had to do.

If I stayed still, I would freeze.

If I kept moving, I might live.

I turned toward the largest vent mouth, where the thermal flow streamed upward in a thin spiral. It led deeper into the rock, carrying the heat with it.

The decision came easy.

Follow the warmth.

Not for comfort. For survival.

The current would be my path now, alive one day, gone the next. But while it flowed, I would trace it.

I lingered one more moment in the chamber, watching the plankton dance in the vent’s breath. The small lights moved with purpose, tracing invisible patterns in the current. Their glow shimmered like language I couldn’t read.

Then I began to move again.

The current tugged me downward first, then out through another passage. The water cooled slightly, but not enough to drive me back. The rhythm of the vent’s pulse stayed steady behind me, like the echo of a heart too large to belong to any creature.

As I swam, I glanced once over my shoulder, toward where Harbour would be.

It was gone from view, buried in the dark. I could almost imagine the hollow empty now, cold stone swallowing the small space I’d once called safety.

I sent a single click into the dark behind me. The echo returned faint, weak.

Harbour still existed. But it no longer waited for me.

That was enough.

The current ahead brightened. Heat brushed my gills again. I followed it without hesitation.

Movement meant memory. Stillness meant loss.

The System woke, lines of light cutting through the dark.

[Objective Added: Trace Thermal Current]

[Body Temp Regulation +0.3%]

[Thermal Variance Rising]

The glow faded. The warmth did not.

I took one last breath through my gills and turned fully into the current.

The path ahead shimmered faintly, twisting like the memory of wind through sails. The plankton streamed with me, bright and wordless.

I didn’t look back again.

Stay still and die. Move and remember.