The detention center looked different at night.
During the day, everything seemed designed to reassure visitors.
Clean corridors.
Uniformed officers.
Cameras mounted above every entrance.
At night, the building showed what it really was.
Concrete.
Steel.
Locked doors.
Hae-in followed Kang through the security checkpoint.
The officer at the desk checked their identification twice.
"Cell Block C?" he asked.
"Yes."
"At this hour?"
Kang showed his badge.
"Investigation."
The officer hesitated.
Then opened the gate.
The lock released with a heavy metallic click.
Hae-in walked through.
She could hear the mechanism closing behind them.
One door.
Then another.
Then another.
She glanced at Kang.
"How many?"
"Three security doors before we reach the block."
"Good."
He looked at her.
"Good?"
"If someone wanted to hide something here, they'd choose somewhere difficult to reach."
"And you think Cell Seventeen is that place?"
"I think the number wasn't written for decoration."
They reached Cell Block C.
Rows of cells stretched along both sides of the corridor.
One through sixteen.
Then—
17.
Hae-in stopped.
The door looked ordinary.
Too ordinary.
She crouched beside the lock.
"What are you looking for?"
"Anything."
She examined the frame.
Scratches.
Old paint.
Nothing.
Then she noticed a thin line near the bottom.
She touched it.
Dust came away on her fingertip.
"What?"
She pointed.
"Someone cleaned this recently."
Kang looked closer.
"The rest of the doors haven't been cleaned?"
"Not like this."
He called an officer.
"When was Cell Seventeen last occupied?"
The officer checked his tablet.
"Three months ago."
"By whom?"
The officer hesitated.
"According to the system, nobody."
Hae-in looked at him.
"Nobody?"
"Cell seventeen has been listed as unavailable."
"Why?"
"Maintenance."
Kang and Hae-in exchanged a glance.
"Since when?"
The officer checked again.
"Eight years."
Silence.
Eight years.
The same year as the seven disappearances.
Hae-in stood.
"Open it."
The officer looked uncomfortable.
"This cell isn't supposed to—"
"Open it."
The lock clicked.
The door moved inward.
The cell was empty.
One bed.
One metal sink.
One toilet.
Nothing else.
Kang entered first.
Hae-in followed.
She immediately noticed the wall.
Four walls.
No windows.
No decorations.
No scratches.
Nothing.
But something felt wrong.
She walked to the bed.
Ran her fingers beneath the frame.
Dust.
Then—
her hand stopped.
There was something taped underneath.
She pulled it free.
A small plastic evidence bag.
Inside was a key.
Kang stared at it.
"That's not supposed to be there."
"No."
Hae-in turned the bag over.
A number had been written on the label.
17–04.
Kang frowned.
"Seventeen dash four."
Hae-in looked around the room.
"Four what?"
Before he could answer, the lights went out.
Complete darkness.
The security alarm didn't sound.
That was worse.
Kang reached for his flashlight.
"Stay behind me."
Hae-in didn't move.
"Kang."
"What?"
"Listen."
They both became still.
Footsteps.
Outside the cell.
Slow.
One.
Two.
Three.
Then silence.
Kang opened the cell door.
His flashlight swept across the corridor.
Nobody.
Hae-in stepped outside.
At the far end of the corridor, a security door was slowly closing.
Kang ran.
Hae-in followed.
They reached it seconds too late.
Locked.
Kang hit the emergency release.
Nothing.
"Someone disabled it."
Hae-in looked back toward Cell Seventeen.
The lights suddenly returned.
Everything was exactly as they had left it.
Except—
the evidence bag was gone.
Hae-in checked her hand.
Empty.
Someone had taken it from her.
While they were standing in the dark.
She looked at Kang.
"They knew we were coming."
He nodded.
"And they wanted us to find the key."
Hae-in's eyes narrowed.
"Then they wanted us to believe it was a key."
She walked back toward Cell Seventeen.
Kang followed.
She looked beneath the bed again.
Nothing.
Then she noticed something on the wall.
A tiny mark.
Four vertical lines.
And beneath them—
one horizontal line.
She touched it.
The paint came away.
Fresh.
Someone had recently written beneath the surface.
Five marks.
A counting system.
Hae-in stepped back.
"Four."
Kang looked at her.
"What?"
"Seventeen-four."
She pointed at the wall.
"Cell seventeen. Four marks."
Then she looked toward the ceiling.
A camera stared down at them.
The red indicator light was off.
Hae-in smiled faintly.
"They weren't counting rooms."
"What were they counting?"
She looked directly into the dead camera.
"People."
The camera light suddenly turned red.
And somewhere inside the detention center—
a printer began running.
One page.
Then another.
Then another.
Kang's phone vibrated.
He looked at the message.
His face changed.
"What?"
He turned the screen toward her.
A photograph had been sent to him.
It showed Cell Seventeen.
Taken from inside the cell.
The timestamp was thirty seconds in the future.
Hae-in stared at it.
Then her phone vibrated.
A message from the same unknown number.
YOU WERE NEVER SUPPOSED TO OPEN THAT DOOR.
Hae-in looked at the cell.
For the first time that night—
she wondered whether they had entered the room...
or whether the room had been waiting for them.