The ground is a mix of rough stone and packed dirt, and the walls look dug by hand. Here and there, water drips from the low ceiling. Electric lights have been spaced out, casting dim yellow pools among patches of shadow.

“Well, this is cozy,” says Mom.

I swallow hard as we start walking. The only way out is through, I tell myself.

“Or, you know, back up those stairs,” says Jacob.

Come on, I think. Where’s your sense of adventure?

“I must have left it up on street level,” he mutters.

Mom and Dad walk on ahead, narrating for the cameras. I glance over at Pauline, who’s focused on where she’s stepping, careful to avoid the shallow pools of water, the muddy dirt patches between stones.

I lean toward her and whisper, “I expected more bones.”

“We haven’t made it to the tombs yet,” she explains, her voice echoing off the low ceiling. “These are only the galleries. Relics from the days when these tunnels served less grim purposes.”

The tunnel twists and turns, sometimes wide enough for two people, and sometimes so narrow we have to walk single file. The Veil presses against my back like a hand, urging me forward.

“You know the only thing worse than a haunted place?” asks Jacob.

What?

“One you can’t easily leave.”

You don’t know it’s haunted, I think, sounding thoroughly unconvinced.

“How can it not be?” he counters. “Have you forgotten George Mackenzie?”

George Mackenzie was one of the ghosts in a cemetery back in Scotland. He didn’t start haunting the graveyard until some vandals disturbed his bones.

That was one man.

But maybe the stories are wrong. Maybe he was already restless.

“And maybe they’re all friendly ghosts down here,” says Jacob, “just having a grand old time.”

Mom pulls out a small box, its surface studded with lights. An EMF meter—a tool meant to register disturbances in the electromagnetic force. Also known as ghosts. She switches it on, but the meter only registers a muffled static as she lets it trail over the wall.

We reach the end of the galleries, and the tunnel opens into a chamber, the walls lined with glass cases, like in a museum. The glass cases hold text and pictures, explaining how the Catacombs came to be. But the thing that catches my eye is the doorway on the other side.

A stone mantel looms over it, the words carved in bold French type.

ARRÈTE! C’EST ICI L’EMPIRE DE LA MORT.

“Stop!” recites Dad, his voice bouncing off the close stone walls. “This here is the Empire of the Dead.”

“Not ominous,” mutters Jacob. “Not ominous at all.”

“In the 1700s,” continues Dad, addressing Annette’s camera, “Paris had a problem. The dead outnumbered the living, and the living had no place to put them. The graveyards were overflowing, sometimes literally, and something had to be done. And so the conversion of the Catacombs began.”

“It would take two whole years,” says Mom, “to move the bodies of the dead. Imagine, a nightly procession of corpse-filled wagons rattling through the streets, as six million dead were ferried from their resting places into the tunnels beneath Paris.”

It’s so weird, watching them like this. The way they transform in front of the camera. They don’t become different people, they just become sharper, louder, more colorful. The same song with the volume turned up. Dad, the image of a scholar. Mom, the picture of a dreamer. Together, “the Inspecters” look larger than life. I snap a photo of them being filmed as Dad goes on.

“For decades,” he says, “the bones of the dead littered these tunnel floors, the remains piled haphazardly throughout the vast tomb. It wasn’t until an engineer by the name of Louis-Étienne Héricart decided to convert the grave into a place for visitors that the real transformation began and the Empire of the Dead was formed.”

Mom gestures, like a showman pulling back a curtain. “Shall we go in?”

“I think I’ll wait here,” says Jacob, suddenly fascinated by the glass cases.

Suit yourself, I think.

I follow the crew forward without looking back. And even though I can’t hear Jacob’s steps, I know he’s there, on my heels, close as a shadow as we step through into a world of bones.

The bones are everywhere.

They line the dirt walls, a sea of skeletons rising almost to the ceiling. They form patterns, rippling designs—a wave of skulls set on a backdrop of femurs, the morbid decorations stacked as high as I can see. Empty eye sockets stare out, and jaws hang open. Some of the bones are broken, crumbling, and others look startlingly fresh. If you squint hard enough, the pieces disappear, and you’re left with a pattern of wavering grays that could be stone instead of bone.

Our shadows dance on the walls, and I take photo after photo, knowing the camera will only capture what’s here, only see the real. But right now, the real is strange enough. Strange, and chilling, and almost—beautiful.

“And horrifying,” says Jacob. “Don’t forget horrifying.”

We round a corner, and as if on cue, the EMF meter in Mom’s hand erupts from static into a high-pitched whine that echoes through the tunnels like a scream.

Mom jumps, and quickly switches the unit back off.

“Well,” she says, her voice a little shaky. “I think that says enough.”

I shiver, unsettled.

Even Pauline is looking tense.

“Gee, what could possibly be making her nervous?” muses Jacob. “Is it the fact we’re five stories underground? Or that this tunnel is roughly the size of a coffin? Or could it be the fact we’re surrounded by six million bodies?”

Six million—it’s a number so big it doesn’t seem real.

Two hundred and seventy—that’s a better number. Still a lot, but countable. Two hundred and seventy is the number of bones you have when you’re born. Some of them fuse together as you grow, so by the time you’re an adult, you have two hundred and six (thanks, Science class).

So, if the Catacombs are home to more than six million bodies, how many bones?

Six million times two hundred and six is—a lot. Too many to capture in a photo. But picture this: It’s enough bones to stack five feet high throughout every one of the tunnels under Paris. An Empire of the Dead as large as the city, the bodies unmarked and unknown.

Jacob begins to sing, and it takes me a solid thirty seconds to realize what he’s singing.

“… the foot bone’s connected to the leg bone, the leg bone’s connected to the knee bone …”

“Are you serious?” I whisper.

He throws up his hands. “Just trying to have a sense of humor about this.”

We wind our way through the tunnels, the locked iron gates converting the maze around us into a clear path. I wonder how easy it would be to get lost without those doors.

“Do you see this line overhead?” asks Dad, the question directed at the cameras as much as us.

I stare up and see a thick black mark painted on the ceiling.

“Back before they installed lights and gates, that was the only way to keep people from getting lost.”