The staircase seemed to have no end.

Milo counted the steps.

Twenty.

Thirty.

Forty.

Then he stopped counting because the numbers had started appearing on the walls.

39.

12.

204.

7.

Poppy noticed them too.

“Those aren’t floor numbers.”

“No,” Elias said.

Milo looked at the talking black cat.

“Then what are they?”

“Dates.”

“Dates?”

Elias nodded.

“Every number belongs to something that was lost.”

Poppy pointed at one.

“204?”

“Year 204.”

“That’s in the future.”

Elias looked uncomfortable.

“Yes.”

Milo stopped walking.

“You mean the museum has lost things from the future?”

“Sometimes.”

Poppy stared at him.

“That is absolutely not normal.”

“Nothing here is.”

They continued downward.

The walls slowly changed from stone to glass.

Behind the glass were strange objects floating in darkness.

A silver crown.

A broken spaceship.

A red rose preserved in ice.

A tiny blue planet.

And a golden key that appeared to be breathing.

Milo stopped.

“What is that?”

Elias glanced at it.

“Don’t touch it.”

“Why?”

“Because it opens whatever door you’re thinking about.”

Poppy immediately stepped away.

“I’m thinking about my bedroom.”

The key suddenly moved inside its glass case.

Poppy screamed.

“STOP THINKING ABOUT IT!”

“I’M TRYING!”

The key began glowing.

Elias quickly slapped a paw against the glass.

The glow disappeared.

“Excellent,” he muttered. “Now everyone stop thinking.”

Milo stared at him.

“How do you know so much about this place?”

Elias continued walking.

“Because I helped build it.”

Milo’s expression changed.

“You said you worked with my grandfather.”

“I did.”

“You built the museum?”

“Part of it.”

“Why?”

Elias didn’t answer.

Poppy whispered:

“That’s usually when people are hiding something.”

Elias sighed.

“I was helping Arthur create a place where lost memories could be stored safely.”

“And did it work?”

“No.”

“What went wrong?”

Elias stopped.

They had reached the bottom.

A massive metal door stood before them.

It had no handle.

Only a single golden eye.

Elias looked at Milo.

“Your grandfather wanted to save everyone.”

Milo frowned.

“Everyone?”

“Every person who had ever been forgotten.”

The eye opened.

A deep voice echoed through the staircase.

“IDENTIFY THE LIVING.”

Elias stepped forward.

“Elias Quinn.”

The eye flashed red.

“REJECTED.”

Elias sighed.

“Still rude.”

Poppy stepped forward.

“Poppy Reed.”

The eye flashed.

“ACCEPTED.”

Poppy smiled.

“See? It likes me.”

Milo stepped forward.

The eye stared at him.

For several seconds, nothing happened.

Then—

“ARTHUR QUINN.”

Milo froze.

“No.”

The voice repeated:

“ARTHUR QUINN.”

Milo shook his head.

“I’m Milo.”

The eye flashed blue.

“ARTHUR QUINN: RETURNED.”

The door opened.

Milo looked at Elias.

“Why does it think I’m my grandfather?”

Elias whispered:

“Because the museum doesn’t recognize names.”

“What does it recognize?”

“Memories.”

They entered.

The room beyond was enormous.

There was no ceiling.

No visible walls.

Only thousands of floating shelves stretching into darkness.

Every shelf contained objects.

But unlike the upper museum, these objects were glowing.

Poppy looked around.

“This is incredible.”

Milo noticed a glass case near the entrance.

Inside was a photograph.

He picked it up.

It showed his grandfather.

Arthur Quinn.

Standing in the museum.

Beside him was Elias.

And between them was a little girl.

Milo’s heart stopped.

The girl was him.

Or rather—

It was impossible.

The girl looked exactly like Milo.

Same eyes.

Same expression.

Same silver pocket watch.

Poppy stared at the picture.

“Why is there a girl?”

Milo turned it over.

A sentence was written on the back.

THE FIRST KEY WAS NEVER A KEY.

Milo touched the photograph.

The room suddenly changed.

He was no longer in the museum.

He was standing in a bedroom.

A young Arthur Quinn was sitting beside a small child.

The child looked frightened.

Arthur held the silver pocket watch.

“Listen carefully,” he said.

The child nodded.

“If the museum ever calls you by my name…”

The child whispered:

“What should I do?”

Arthur looked directly at her.

“Run.”

The memory ended.

Milo gasped.

Poppy grabbed his shoulder.

“What did you see?”

“My grandfather.”

“What was he saying?”

Milo looked at Elias.

“Who was that child?”

Elias remained silent.

“Elias.”

Nothing.

“Tell me.”

The cat lowered his head.

“It was your mother.”

Milo froze.

“My mother?”

“Yes.”

“But that picture…”

“She was young.”

“Why did she have my watch?”

“Because Arthur gave it to her.”

Milo touched the pocket watch.

“Why?”

Elias looked toward the darkness.

“Because your family has been connected to this museum for generations.”

Suddenly, a bell rang.

DONG.

The shelves shook.

Poppy looked upward.

“What was that?”

Elias whispered:

“Someone has entered.”

“Who?”

Elias looked terrified.

“Arthur.”

A figure appeared at the far end of the room.

An old man.

Gray hair.

Long black coat.

Silver ring.

Milo stopped breathing.

“Grandpa?”

The man smiled.

“Milo.”

Milo took a step forward.

Elias shouted:

“Don’t!”

The old man laughed.

“You still don’t trust me, Elias?”

Elias’s fur stood up.

“You died.”

Arthur smiled.

“Did I?”

Milo stared at him.

“Where have you been?”

Arthur walked closer.

“Waiting.”

“For what?”

“For you.”

Milo looked at Poppy.

She whispered:

“Something is wrong.”

Arthur stopped.

“What did you say?”

Poppy stepped backward.

“I said nothing.”

Arthur smiled.

“You always were observant.”

Milo’s eyes narrowed.

“You know Poppy?”

Arthur’s smile disappeared.

“Of course.”

“But you’ve never met her.”

The old man remained silent.

Milo understood.

“You’re not my grandfather.”

Arthur’s face changed.

His skin cracked like old paper.

His eyes became black.

His smile stretched far too wide.

Elias shouted:

“RUN!”

The creature lunged.

Milo grabbed Poppy.

They ran between the shelves.

Behind them, the creature screamed:

“YOU CANNOT HIDE FROM WHAT YOU HAVE LOST!”

The shelves began collapsing.

Objects flew through the air.

A giant red balloon chased Poppy.

A sword chased Milo.

A screaming violin followed Elias.

“Why is everything attacking us?” Poppy shouted.

Elias ran beside them.

“Because the museum thinks we’re thieves!”

“We didn’t steal anything!”

“You exist here!”

“How is that stealing?”

“Apparently that’s enough!”

Milo spotted a small door ahead.

He grabbed the handle.

Locked.

He looked at his pocket watch.

The symbol began glowing.

Milo pressed it against the door.

Click.

The door opened.

They rushed inside.

The room was tiny.

There was only one object.

A mirror.

Milo looked into it.

His reflection stared back.

Then it smiled.

Milo didn’t.

Poppy gasped.

The reflection raised its hand.

It wrote something on the mirror with its finger.

MIDNIGHT IS NOT A TIME.

Milo stepped closer.

The reflection wrote another sentence.

IT IS A PLACE.

Then the mirror cracked.

A voice whispered from behind them.

“You finally understand.”

Milo turned.

Arthur stood in the doorway.

But this time he looked normal.

Human.

Tired.

Sad.

“Grandpa?”

Arthur nodded.

“Yes.”

Elias stared at him.

“You’re alive?”

Arthur smiled faintly.

“No.”

Milo’s heart sank.

“Then what are you?”

Arthur looked at the mirror.

“A memory that has been waiting too long.”

He pointed toward the glass.

“Your real grandfather is trapped on the other side.”

Milo stared.

“How do I get him out?”

Arthur’s expression became serious.

“You don’t.”

“Why?”

“Because if you open the door…”

He looked toward the ceiling.

“…something else will come through.”

The museum suddenly began shaking.

A deep growl echoed beneath them.

Poppy whispered:

“What is that?”

Arthur looked terrified.

“The thing your grandfather locked away.”

The floor cracked open.

A giant eye appeared beneath the museum.

Then another.

Then hundreds.

Arthur grabbed Milo’s shoulders.

“Listen to me.”

“What?”

“Whatever you hear…”

He looked directly into Milo’s eyes.

“…do not answer when it calls your name.”

From beneath the floor came a whisper.

Soft.

Familiar.

“Milo…”

Milo froze.

The voice came again.

“Milo Quinn…”

Poppy grabbed his hand.

“Don’t answer.”

Milo stared into the darkness.

Then a final voice rose from below.

It sounded exactly like his own.

“I’m waiting for you.”

The lights went out.

And somewhere beneath the museum…

a door unlocked.