“What exactly are you doing?” asks Jacob as my cheeks flush from the heat.

So far the only warning I have that the poltergeist is near is that flush of cold. I want to be sure I can feel it.

“You’re turning yourself into a ghost thermometer.”

I pull the sleeves down over my hands. Basically.

The lights flicker overhead, and I nearly jump out of my seat. But there’s no flash of cold, no warning chill, and a second later the lights come back on.

“That happens sometimes on trains,” says Mom, scooting closer. “But don’t worry. I doubt this car is haunted.”

She says it breezily, but my stomach tightens, a reminder that the poltergeist isn’t the only thing I have to worry about. The Veil is still ebbing and flowing around me, ready to drag me under the second I let my guard down. Jacob inches closer until our shoulders almost touch.

“Not on my watch,” he says.

We get off at a station called Opéra and step onto the street in front of a giant stone building with more piping than a wedding cake. This, according to Dad, is the Palais Garnier. The Paris Opera House.

“I thought The Phantom of the Opera was just a Broadway show,” I say.

“It is,” says Dad.

“But you’re saying there really is a phantom here?”

“I’m saying there’s a story.”

“Most tales are inspired by something,” says Mom, craning her neck.

We walk inside the opera house. The entire gallery is made of marble, the swirls of white-and-gray stone interrupted only by massive iron candelabras. The stairs are straight out of Hogwarts, giant steps that split off to the left and the right, as if leading up to the house common rooms. As we step into the auditorium, Jacob lets out a low, appreciative whistle. It’s full of red velvet seats and balconies, every surface covered in gold.

Mom, Dad, Pauline, and the crew head down into the chambers beneath the opera. I decide to sit this one out, sinking into one of the velvet seats with the leftover macarons from yesterday. Dad shoots me one last stay put look as they retreat down the aisle.

I watch as a handful of workers onstage maneuver pieces of a set. I get glimpses of the unfinished bits, the cables and ropes and undersides exposed. Soon, the set pieces come together into what looks like the front of a mansion.

“This is nice,” says Jacob, perching beside me. “We should do this more often, the whole not-looking-for-ghosts thing.”

“We’re not not looking for ghosts,” I say, thoughts turning.

Every crack of the stagehand’s hammer, every scrape of wood, every creak and groan puts me on edge.

When my cell rings, I yelp in surprise and bang my knee against the arm of the seat.

I answer, rubbing my shin. “Hey.”

“Is for horses,” chides Lara.

“What?”

“Never mind, just something my mother says. Can you talk? Where are you?”

“The opera.”

“Oh, have you seen the phantom? There are actually several. Uncle told me to leave them alone, though—they weren’t causing any trouble, and apparently a few ghosts can be good for business. Don’t know if I agree with him, but I figured the phantoms could wait till my next school trip.”

Jacob clears his throat.

“Anyway,” says Lara pointedly, “do you want the bad news, or the bad news?”

“I don’t think that’s how the saying goes,” comments Jacob.

“Well, it’s how it goes now. Because we—or rather you—have a very large problem.”

“Great,” I say, because I don’t seem to have enough of those. “Care to explain?”

Lara clears her throat. “Remember how I said poltergeists are stronger than normal ghosts because they aren’t bound to the Veil?”

“Yes.”

“And as you already know, the Veil is tailored to fit the ghost, the place they died, which means it’s essentially tied to the ghost’s memory—that’s what binds it there. So if a poltergeist isn’t bound to the Veil, it’s because—”

“They don’t remember,” I say as it hits me.

Lara exhales. “Exactly. That’s why the mirror didn’t do anything to stop him. A reflection only works on ghosts because it shows them what they already know but simply haven’t accepted.”

Watch and listen. See and know. This is what you are.

“But if someone showed you something you didn’t remember,” continues Lara, “it wouldn’t have the same impact on you.”

“But if the mirror doesn’t work,” says Jacob, “how are we supposed to stop him?”

“It doesn’t work,” says Lara, “because he doesn’t remember who he was. Which means you have to remind him.”

“And how are we supposed to do that?” I ask. “It’s not like we have any clue who he is—was.”

“Well,” says Lara, “what do you already know about him?”

“Nothing,” I hiss, exasperated.

“Don’t be ridiculous. You’ve seen him, haven’t you? What does he look like?”

I close my eyes, trying to summon the only clear image I have, from the moment I was balanced on top of the grave. “He was short, only came up to my shoulder.”

“Okay, so he’s young.”

“He had brown hair. Old-fashioned clothes.”

“What kind of old-fashioned?”

“I don’t know,” I say. “The kind with buttons.”

Lara makes a short, exasperated sound. “Well, next time, pay more attention. Every detail is a clue. What he looks like, when he started following you, what he said—”

“Wait,” says Jacob. “He did say something. Remember, Cass … ?” Jacob trails off, trying to sound out the words. “Un, du, twa, something about a ‘cat sank’ …” he fumbles, then adds, “The last word was definitely dees.”

“Well done, ghost,” says Lara grudgingly. “All right, that’s interesting.”

“Do you know what it means?” I ask.

“He was counting,” says Lara. “Un, deux, trois, quatre, cinq, six, sept, huit, neuf, dix. That’s one through ten in French.” She lowers her voice, talking to herself as much as us. “But why would he be counting up instead of down?”

“You speak French?” I cut in.

“Of course,” says Lara briskly. “And German. They make us take two foreign languages in school. I also know a little Punjabi, thanks to my dad. My parents say language is the most valuable currency. Don’t you know any other language?”

“I know how to ask for the bathroom in Spanish,” offers Jacob.

“Um.” I chew my lip. “I memorized all the incantations in Harry Potter.” I look at Jacob. “And I can speak to ghosts.”

“Obviously not,” says Lara, “or you wouldn’t need me to translate. Look, until we find out who this poltergeist is—was—you don’t stand a chance of winning.”

“Thanks for the confidence,” I mutter as the film crew reappears, Mom and Dad in the lead. Anton and Annette follow, cameras hoisted on their shoulders as my parents make their way down the aisle toward the stage. They’re shooting B-roll, the snippets of footage that will go behind a voiceover, help set the scene.