The siren started mid-afternoon.
A shrill, mechanical wail—not like the city sirens of the old world, but a precise, internal alert coded directly into RAIN, Kim Jisoo's custom lab AI. The sound jolted through the lab like a needle under the skin, impossible to ignore.
Jisoo was halfway through reviewing atmospheric logs when it hit.
He didn't freeze. Didn't panic.
He stood up fast, walked to the terminal, and silenced the alarm manually.
[ALERT: Unauthorized Movement Detected in Perimeter Zones 3–7][Visual Feed Engaged]
By then, Haru and Ji-won were already at the lab entrance, blinking sleep from their eyes. The boy clutched a half-unzipped blanket around his shoulders, and the old woman looked uneasy, one hand steadying herself on the doorframe.
Jisoo didn't speak as he brought the footage onscreen. The main wall monitor lit up with multiple angles from hidden cameras placed across a wide radius outside the mountain—covering parts of the city and nearby residential blocks.
At first, it was just motion.
Then came the people.
Dozens of them.
Moving in slow, strange patterns. Some walked with stiff limbs, like puppets. Others twitched or jolted like their bodies didn't fit properly.
They were entering houses. Not knocking. Not waiting. Just… going in.
One camera feed showed a man breaking a window with his bare hand, blood running down his arm like it didn't matter.
Another showed a group—three adults—standing at a family's door. Waiting. Then pushing inside once the door opened.
No talking. No shouting.
Just action.
The screen glowed with the horror of quiet invasion.
"They're… going into homes?" Ji-won asked, voice low and tight.
Jisoo said nothing.
He was already pulling up the solar report.
[SOLAR INTENSITY: 6.4% - DIM LEVEL CRITICAL][ADJUSTED SPECTRUM: UV-A NEAR ABSENT][VISIBLE LIGHT SPECTRUM COLLAPSING]
His eyes narrowed. His fingers tapped faster.
Six percent.
The sunlight was barely hanging on. The spectrum was breaking apart. The sky itself seemed to be unraveling.
Jisoo turned away from the monitor and stared at the whiteboard on the side wall. It was mostly clean, only a few notes from earlier analysis.
Now he grabbed a marker and began to write:
1. Sunlight = Barrier?2. Transformation = Triggered by Dimming?3. BUT: Why not Night? Why didn't it start earlier?
He circled the last line.
Night had always been dark. Always been the natural realm of fear. But the world had never seen transformation like this before—not until now, when the sun was fading.
That was the key difference.
Not darkness.
Sunlight itself.Or the lack of something in it.
He wrote again:
4. Something inside sunlight prevents activation? Not darkness that causes change—but loss of protection?
Ji-won sat down slowly near the corner, silent, watching him. Haru remained closer to the screens.
Jisoo wiped sweat off his temple with his sleeve. His mind raced through years of data he'd studied. Solar physics, radiation filtering, vitamin D absorption, circadian rhythms, UV mutation—something had to explain this shift.
The transformation of the people—those things—they didn't move like infected. They weren't sick. They were altered.
He turned to check the feed again—
—and then it happened.
A scream tore through the lab.
"Noo!"
Jisoo snapped around.
The boy was pointing—arm stiff, finger trembling—right at Ji-won.
"Her eyes!" Haru shrieked. "Something's wrong! Her eyes!"
Jisoo froze. He turned slowly.
Ji-won looked at them both, her face calm.
Too calm.
Then she smiled.
It was subtle. Almost gentle.
But the corners of her mouth twitched a little too much. Her eyes, once soft with age and sadness, shimmered now—not black, not fully—but something… unfocused.
Like her gaze was no longer hers.
Jisoo took one step back.
His body tensed. Knife instinctively in hand.
Haru clutched the back of Jisoo's coat, trembling behind him.
Ji-won tilted her head.
"I'm fine," she said, voice light.
Too light.
Not wrong, exactly—but hollow.
As if something else was trying to wear her voice, like a child wearing adult clothes.
Jisoo didn't speak.
He just watched.
Ji-won's eyes blinked once. Slowly.
Then again. Faster.
The shimmer faded.
She looked confused.
"What… what's wrong?" she whispered, voice suddenly hoarse.
Jisoo didn't relax.
"Where are you?" he asked.
Ji-won blinked.
"…what?"
"Do you know where you are right now?"
She glanced around. Her gaze finally sharpened.
"I'm in your lab. You… you brought us here."
She looked at Haru, who was still holding on to Jisoo like the world would shatter.
"…Why is he looking at me like that?" she asked.
Jisoo watched her carefully.
The shimmer was gone.
For now.
But something had changed.
"I think…" he said slowly, "…it tried to get into her."
Haru looked up at him, eyes wet. "Can it do that? To her?"
"I don't know."
He walked over to the desk and grabbed the scanner—an infrared and neural rhythm device he'd built himself, mostly for environmental readings. He modified it once, to check for radiation signatures in living tissue.
He pointed it at Ji-won.
The bar lit up green.
Then flickered yellow.
Then back to green.
Not infected.
But… not completely untouched.
"Sit," he said.
Ji-won obeyed quietly.
He handed her a thermal blanket and opened a canister of electrolyte fluid. She drank without question.
Jisoo turned to Haru.
"You did the right thing."
The boy didn't answer.
He looked shaken, but not broken.
There was steel in his bones. Jisoo saw it.
And yet… even steel bent under the wrong pressure.
He walked to the whiteboard again.
Wrote one more line:
5. Light protects consciousness? Or delays loss?
Then underneath, a single word:
TEST.
He would need to test the light levels in the lab.
Control light spectra in sealed rooms.
Maybe even…
He looked at Ji-won.
No. Not unless absolutely necessary.
He had limits. He wasn't going to cross them unless there was no other way.
Not yet.
But the rules were changing.
And now he knew one thing more:
Even here, in this lab, they weren't safe.
Not if the sunlight kept dying.
Not if whatever was outside… could reach inside people's minds.
The room was silent again.
But Jisoo's heart wasn't.
It pounded with dread.
With questions.
With the knowledge that the world outside wasn't the only thing being rewritten.
Humanity itself was on the verge of becoming something else.
And they had only hours, maybe days, to understand what.