Paris was drenched in rain that night.
Raindrops fell nonstop over the Louvre Museum's massive glass pyramid. The museum, packed with tourists from around the world during the day, had fallen eerily silent as midnight approached.
That day, too, countless people had crowded around a single painting.
The most famous portrait in the world.
The Mona Lisa.
People stood in long lines just to see the small painting. Some held their phones high, some carried children on their shoulders, and others gasped the moment they stepped in front of it.
But very few people actually gazed at her face for long.
It took only a few seconds to snap a picture and turn away.
For five hundred years, the Mona Lisa had watched countless people pass before her.
People talked endlessly about her smile.
Some called it the smile of a happy woman. Others said it was the expression of someone gazing at the person she loved. Some insisted she was hiding sorrow, while others claimed Leonardo da Vinci had painted his own face as a woman.
But they were all wrong.
There was another reason for her smile.
That smile was neither happiness nor love.
It was the last signal of someone who had spent five hundred years waiting for somebody to find her.
11:47 p.m.
The last visitor left the museum.
“First floor clear.”
A guard's voice came through the radio.
Night guard Pierre walked down a long corridor, flashlight in hand.
Now sixty-two, he had worked at the Louvre for seventeen years.
When he first got the job, everything had seemed fascinating. His friends were envious simply because he got to see world-famous masterpieces every day.
But after seventeen years, that had changed.
Even paintings worth tens of billions of won were nothing more than familiar scenery at work to him.
The painting he had seen most often was the Mona Lisa.
As he passed through the Mona Lisa Gallery, Pierre said out of habit,
“Good work today, ma'am.”
Of course, there was no answer.
Pierre gave a small snort of laughter and turned away.
That was when it happened.
Knock.
A faint sound reached him.
Pierre stopped walking.
“Huh?”
It sounded a little like water dripping from the ceiling.
But this was the finest museum in the world. In a gallery where the temperature and humidity were rigorously controlled, there was no way rainwater could be dripping.
He started walking again.
Knock.
This time, it was clearer.
Pierre turned around.
There was no one there.
Only the Mona Lisa gazed at him from behind the bulletproof glass.
“Did a rat get in?”
He switched on his flashlight and searched around the walls.
Then he felt something strange.
Something was different.
Pierre looked at the Mona Lisa again.
It was a face he had seen almost every day for seventeen years.
The eyes.
The nose.
The lips.
The folded hands.
The river and mountains in the background.
Everything was exactly the same.
And yet…
Pierre took one step forward.
“Wait.”
The Mona Lisa's eyes were strange.
Usually, they seemed to stare straight at the visitors. But now, they were turned toward the lower right.
In exactly the direction where Pierre was standing.
A chill ran down his spine.
“I must be tired.”
Pierre rubbed his eyes.
Then he looked again.
Everything was normal.
He let out a relieved sigh.
“Getting old must be making me see all kinds of things.”
He was about to turn away.
Knock.
Knock.
Knock.
This time, there was no doubt.
The sound had come from the painting.
Pierre couldn't move.
Knock.
Knock.
It sounded as if someone were tapping on the glass from the inside.
Pierre turned his head very slowly.
And froze.
The Mona Lisa's right hand was moving.
From the hands that had been folded together, her index finger slowly rose.
The finger pointed toward the bulletproof glass.
Knock.
The Mona Lisa tapped on the glass from inside the painting.
The color drained from Pierre's face.
“Wh… who's there?”
It was a ridiculous question even as he said it.
How could anyone be inside a painting?
But the Mona Lisa moved her finger again.
And this time, even her lips began to move.
The lips that had held a smile for five hundred years slowly parted.
Pierre tried to scream, but no sound came from his throat.
The Mona Lisa spoke.
“Help me…”
Her voice was barely audible.
But Pierre heard it clearly.
“What did you say?”
Without realizing it, he stepped closer to the painting.
Her eyes were filled with fear.
“Find me…”
“Who are you?”
The Mona Lisa's lips trembled.
“I am…”
At that moment, the gallery lights flickered.
Once.
Twice.
Then they went out completely.
Pitch-black darkness.
Pierre hurriedly switched on his flashlight.
The light illuminated the painting again.
The Mona Lisa wasn't moving.
She was back to normal.
Pierre gasped for breath.
“It was a dream. It had to be a dream.”
Then a single tear slipped from the Mona Lisa's eye.
Pierre held his breath.
The tear ran down her cheek.
But then something astonishing happened.
The tear didn't stop inside the painting.
It passed through the bulletproof glass and flowed outside.
Plink.
It hit the floor.
And where the tear fell, a small golden object appeared.
Pierre picked it up cautiously.
It was a round metal disk, slightly larger than a coin.
A triangle-and-eye symbol was engraved on the front.
An old Italian inscription was written on the back.
Pierre took out his phone and held it up to the translation app.
A moment later, a sentence appeared on the screen.
‘The day her smile fades, the door will open.’
“What does that mean?”
Just then, the Mona Lisa opened her mouth again.
“Leonardo… hid it.”
“Leonardo?”
Pierre repeated.
“Leonardo da Vinci?”
She gave a tiny nod.
“What did he hide?”
The Mona Lisa's eyes turned toward the lower right of the painting.
“The truth…”
Suddenly, the alarm rang throughout the museum.
Screeeeech!
Pierre jumped and grabbed his radio.
“Security control room! What's going on?”
Static crackled in response.
“Pierre!”
It was his colleague Jean, his voice frantic.
“Movement detected in the underground storage room.”
“An intruder?”
“I don't know.”
“The cameras?”
“They're not working.”
Pierre looked at the Mona Lisa.
“Which storage room?”
There was a brief silence on the other end of the radio.
“B-17.”
Pierre's expression hardened.
B-17.
It was a place surrounded by strange rumors even among the staff.
A small room accidentally discovered thirty years earlier during construction work beneath the museum.
Officially, it was said to be an old plumbing facility, but for some strange reason, the entrance had been sealed ever since.
“No one can get into that room.”
“Exactly. That's the problem.”
At that moment—
Click.
A sound came from directly in front of Pierre.
It was the wall where the Mona Lisa had been hanging.
Part of the wall, painting and all, began slowly moving forward.
“Oh my God…”
A black space appeared behind the wall.
Even Pierre, who had worked there for seventeen years, had never seen it before.
He shone his flashlight inside.
A small wooden box sat within.
There was barely any dust on it.
It looked as if someone had placed it there only moments ago.
Letters were engraved on the lid.
L. da Vinci
Pierre's hand trembled.
“Leonardo da Vinci…”
He pulled out the box.
There was a round recess in the center of the lock.
Pierre looked at the golden disk in his hand.
It was exactly the same size.
“No way…”
He fitted the disk into the recess.
Click.
The box opened far too easily, as though it had been waiting five hundred years.
Inside were a small silver key and a worn piece of parchment.
The parchment was covered in writing reversed left to right, like a mirror image.
Pierre knew about it.
Leonardo da Vinci had actually used mirror writing.
He photographed the writing with his phone, then flipped the image horizontally on the screen.
A few words became legible.
Lisa.
Firenze.
And…
Vita.
Life.
Pierre's heart began to pound.
At the very bottom of the parchment, one sentence was written much larger than the others.
He entered it into the translation app.
The translation appeared on the screen.
‘The Mona Lisa is not a painting.’
Pierre froze.
Beneath it was a smaller sentence.
‘She is alive.’
“That can't be…”
At that moment, the woman in the painting moved again.
This time, she wasn't smiling.
The mysterious smile that had captivated the world for five hundred years was slowly fading away.
Only fear remained on the Mona Lisa's face.
“We don't have much time.”
Pierre asked,
“Time for what?”
“They're coming.”
“Who?”
The Mona Lisa's eyes shifted toward the space behind Pierre.
Pierre slowly turned around.
There was no one there.
But footsteps echoed from the darkness at the end of the corridor.
Click.
Click.
Click.
It wasn't just one person.
There were several.
Pierre shone his flashlight ahead.
He saw nothing.
“Who's there?”
There was no answer.
Only the footsteps drawing closer.
The Mona Lisa spoke.
“Hide the key.”
Pierre hurriedly slipped the silver key from the box into his pocket.
“What is this key?”
“The key that opens the door.”
“What door?”
The Mona Lisa didn't answer.
Instead, for the first time, she looked straight at Pierre.
“Get me out.”
Pierre wondered if he had heard her correctly.
“You want me to get you out of the painting?”
“I'm not inside the painting.”
“Then where are you?”
She opened her mouth.
But just before she could answer, all the lights came back on.
Pierre squinted.
And when he opened his eyes,
The painting had returned to normal.
The hidden wall was closed.
The wooden box was gone.
Everything looked as though it had never existed in the first place.
Everything except one thing.
The silver key in Pierre's pocket.
Then his radio crackled.
“Pierre! Do you copy?”
“I hear you.”
“The B-17 door is open.”
Pierre swallowed.
“What?”
“The door that's been sealed for thirty years opened by itself.”
Pierre broke into a run.
He took the elevator down to the basement and headed for the B-17 section.
When the elevator doors opened, cold air brushed across his face.
A massive iron door stood at the end of the corridor.
It was half open.
His colleague Jean was waiting there.
“Strange, isn't it?”
Pierre didn't answer.
The two of them carefully stepped inside.
There was nothing in the room.
Only an old stone staircase along one wall.
The stairs descended deep underground.
“There was a place like this beneath the Louvre?”
Jean asked.
Pierre shook his head.
They descended the stairs.
Ten steps.
Twenty steps.
Fifty steps.
No matter how far they went down, they couldn't see the end.
At last, a massive stone door appeared.
There was a small keyhole in the center.
Pierre touched the silver key in his pocket.
It looked like it would fit perfectly.
“Pierre.”
Jean pointed at the wall.
An old painting had been carved into it.
It was the face of a woman.
The two men held their breath at the same time.
It was the Mona Lisa.
But something was wrong.
The woman in the painting wasn't smiling.
Instead, her eyes were wide open, and she was crying.
A Latin sentence was carved beneath her.
Pierre opened the translation app.
‘The true woman lies sleeping below.’
At that exact moment, a sound came from beyond the stone door.
Boom.
The two men stepped back.
Boom.
This time, it was louder.
It sounded as if someone were pounding on the door from the other side.
Then, very faintly, a woman's voice reached them.
“Open… please.”
Pierre froze.
That voice.
It was the exact same voice he had heard from the woman in the painting moments earlier.
He pulled out the silver key.
Jean grabbed his hand.
“Where did you get that key?”
Pierre couldn't answer.
At that moment, another voice came from beyond the stone door.
This time, it was a man's voice.
Low and ancient.
“Do not open it.”
Pierre and Jean looked at each other.
The woman's voice came again.
“Please…”
The man said,
“If you open the door, she will not be the only one to come out.”
Silence hung in the air for a moment.
Then the final words followed.
“What has been imprisoned with her for five hundred years will come out too.”
The men's faces stiffened.
Meanwhile, in the empty Mona Lisa Gallery,
A very slow change was taking place behind the bulletproof glass.
The smile had completely vanished from the Mona Lisa's face.
And below the painting,
letters that had not existed for five hundred years began appearing one by one, like black paint.
Find me.
A few seconds later, a second sentence appeared beneath it.
But whatever you do, don't open the door.
Pierre still hadn't seen the message.
The silver key was already in his hand.
And the tip of the key was…
sliding into the stone door's keyhole.
Click.
The door that had been locked for five hundred years began to open.