There’s also the series of shots I took from the bedroom window of my hotel room when Thomas appeared on the street below. I remember him vividly, standing there, his red eyes tipped up. In the photo, though, the street looks empty, the sidewalk marked only by the ghost of a ghost of a ghost, a shadow against shadows, so faint no one else would know.

And then there’s the photo I took of Jacob, sitting atop the broken angel in Père Lachaise. The statue is striking in black and white, but the air over its shoulder is hardly empty. Instead, it bends like candle smoke, like the afterimage of a flash when you blink, ghosted onto the mottled branches between the tombstone and the sky.

It forms the shape of a boy, one knee drawn up, his face caught in the motion of turning away.

There’s no question, Jacob is getting clearer, too.

He moves toward me, and I tuck the photographs back in the folder before he reaches me. Pauline is coming, too. She kisses me twice, once on each cheek.

“It was nice to meet you, Cassidy.”

“Well, Pauline,” asks Dad, “did we make a believer out of you?”

She glances at me, her mouth drawing into a small smile. “Perhaps,” she says. “I will admit, there’s more to this world than meets the eye.”

We gather up our things, say goodbye to the Hotel Valeur (and the desk clerk, who seems particularly glad to see us go), and step out into the Paris sun.

As we make our way to the Metro, I can’t help but look down at the sidewalk and remember how much history, how many secrets, is buried beneath our feet.

“If you had to sum up Paris in one word,” says Mom, “what would it be?”

Dad considers, then says, “Overwhelming.”

“Enchanted,” counters Mom.

“Haunted,” offers Jacob dryly.

I think for a moment, but in the end, I find the perfect word.

“Unforgettable.”

As we wait for the train to the airport, Jacob wanders up and down the platform. I watch as he amuses himself by bobbing a child’s balloon, putting his hand through a musician’s amp as they lean against a pillar, playing guitar. He seems happier, lighter, after sharing his story. I feel a little heavier after hearing it, but that’s okay. That’s how friendship works. You learn to share the weight.

I stick my hands in the pockets of my jeans and feel the edge of something solid and square. I draw it out and freeze. It’s the data card I stole from the footage case, the one marked CAT for Catacombs. My heart thuds as I look over at Mom and Dad, who are standing together and talking a few feet away. I walk over to the nearest trash can, dropping the card inside.

That’s when I notice the man.

He’s standing on the opposite platform, the gulf of the tracks between us, and the first thing I notice is how still he is amid the sea of people.

He looks like a thin shadow in a black suit. He wears white gloves and a black hat with a brim that covers his face.

Until he raises his head, and then I see it isn’t a face at all but a mask. Smooth and white as bone. And a shiver runs through me, because the contours and angles are the same I saw a thousand times down in the Catacombs.

The mask is a skull.

Somewhere behind the open sockets there must be eyes, but I can’t see them. It’s as if he’s wearing a second mask under the first, one that’s solid black, erasing all his features.

My fingers go to the camera around my neck. I can’t take my eyes off him.

He’s so out of place amid the tourists with their suitcases and summer clothes that at first I think the man must be a street performer, one of those who stand perfectly still until you drop a coin into their bowl. But if he’s performing, nobody seems to notice. In fact, the people on the platform move around the man like water around a rock. As if they don’t even see him.

But I do.

“Jacob,” I whisper, but he’s too far away.

I raise the camera to snap a shot, but as I do, the man looks at me. He lifts a gloved hand to his mask, and suddenly I can’t move. My limbs are frozen, my legs dead weight, and as he pulls the mask from his face, all I see is darkness.

My vision flickers, and my lungs flood with cold water.

The Metro disappears and the platform falls away beneath my feet and I fall, plunging down, down into the icy dark.

Everything is gone.

And then it’s back. The world fills with sound, worried voices, fluorescent light. I’m on the ground, gasping, and I feel like I’m about to spit up river water. But there’s only air, and the cold hard surface of the platform beneath me.

Jacob is kneeling on one side of me, and Dad is on the other, helping me sit up. Mom is punching a number into her phone, her face awash in fear. I’ve never seen her afraid. Not seriously. Other people are gathering, murmuring to themselves in quiet French, and I blush, suddenly self-conscious.

“What happened?” I ask.

“You fainted,” says Dad.

“Dropped like a stone,” adds Jacob.

Like the ground was gone.

Like I was falling.

“There’s no signal,” mutters Mom, her eyes glassy with tears.

“I think she’s okay,” says Dad, putting his hand on her arm before turning back to me. “Hey, kiddo. You all right?”

I get to my feet, and Mom wraps her arms around me. I spend the next couple of minutes assuring my parents (and Jacob) that I’m okay, that I just got light-headed, that I’m more embarrassed than hurt. And that last part, at least, is true. There’s a dull ache where my knee hit the ground, and a bad feeling in my chest.

Then I remember. I stiffen, my eyes going instantly back to the place where the shadow stood on the opposite platform. But the man in the black suit with the wide brim hat and the skull mask is gone.

I swallow, the taste of the river still in my throat. Jacob follows my gaze across the platform, reading my thoughts, my questions.

Did you see him? I ask.

Jacob shakes his head. “Who was he?”

I’m … not sure.

But whoever the guy was, he’s gone, and so is the faint, dizzy feeling. And yeah, that was weird. But it’s not the weirdest thing to happen to me this year … or this month … or this week.

Mom and Dad are still studying me, shooting me nervous looks, ready to catch me if I fall. But I feel fine now. Really, I do. I make a note to tell Lara about it later.

By the time the train pulls into the station, the whole thing feels like a dream, far away, just as silly and just as strange. I put it away, in the back of my mind, as the train doors open and we climb aboard. The Blake family: two parents, a ghost-seeing girl, her dead best friend, and a rather unhappy cat.

Jacob perches on a piece of luggage, I lean against Mom, and Dad rests a hand on my head as the train doors slide shut on the platform, and on Paris.

The train pulls out of the station into the dark tunnel, and I adjust the camera on my shoulder, excited to see what happens next.

Turn the page for a sneak peek!

People think that ghosts only come out at night, or on Halloween, when the world is dark and the walls are thin. But the truth is, ghosts are everywhere. In the bread aisle at your grocery store, in the middle of your grandmother’s garden, in the front seat on your bus.