"There's only one way to find out," he said.

Before I knew what was happening, Noah grabbed the top rung, and in an elegant swoop, lifted himself up and over the gate, landing on the other side.

Wiping his hands on his pants, he let out a breath and stood up. "Now you."

He braced himself to help me climb up, but instead, I grabbed the bars and stuck one leg through, and then another, contorting my body until I had squeezed through to the other side.

There were stray cats everywhere. Creeping between the crevices of the foundation, crouching beneath the bushes, peering out from underneath the front stoop as we approached the front door.

"Are you just going to knock on the door?" I asked.

"Do you have a better idea?"

I didn't, but something about it made me feel uneasy. A cat darted across the lawn in front of my feet. I covered my mouth before the gasp came out.

Noah took my hand and squeezed it, and together we climbed up the steps. I braced myself against the railing as Noah pressed the bell.

Somewhere inside, a chime sounded, but no one came to the door. A calico cat rubbed its head against my ankle; I nudged it away. Just as Noah held his finger up to the buzzer again, we heard footsteps thud inside. The sound of locks being unlatched. And then the k.n.o.b turning.

The door opened a crack, and a woman appeared, peeking through the chain bolt. She was holding a shovel, its tip pointed at us through the gap. The foyer behind her was dark.

When I saw her face, I froze. "Miss LaBarge?"

She paused before answering. "Who are you?"

The calico cat slipped inside through Miss LaBarge's legs. "It's me," I said, unable to comprehend why she didn't recognize me. "Renee. From philosophy cla.s.s last year?"

"How did you get in?"

"I squeezed through the bars," I said, putting my hand on the door frame. Miss LaBarge jolted at my advance.

"What do you want from me?" she asked, wedging the tip of the shovel deeper into the gap.

I searched her face, baffled. Maybe she had lost her memory. Maybe that's why she was acting this way. "I don't want anything. I-I didn't know you were going to be here. But now that you are, I just-I'd like to talk to you. Everyone thinks you died." I lowered my voice. "It was on the news. I went to your funeral. I watched my grandfather bury you in the ocean. But now you're here."

She looked at me, and then at Noah. "You're both students at Gottfried?"

"Lycee St. Clement," Noah said.

"What are your names?" she asked.

"Renee Winters," I said.

"Noah Fontaine."

Miss LaBarge squinted at me, as if trying to see something she hadn't seen before. "Winters? The daughter of Lydia and Robert?"

I loosened my grip on my bag. "Yes," I said, confused. "You knew them."

Without warning, she receded into the darkness.

"Wait!" I yelled, but it was too late. She had already shut the door.

I rang the bell again and then collapsed with a sigh on the edge of a cement pot by the railing. A black cat that had been sleeping inside hissed and jumped out. "I don't understand," I murmured, looking up at Noah.

He put a finger to his lips. On the other side of the door, I heard something clicking, and then just as abruptly as it had closed, the door reopened.

"Get inside," she said, her eyes darting about the quiet street behind us as we shuffled past her.

The convent was dark and drafty. After bolting the locks, Miss LaBarge gave us a quick glance. She led us through a series of rooms, each one spa.r.s.ely decorated with little more than a table and a few chairs. There were cats everywhere-curled around the banister, stretching on the windowsills, yawning from beneath the radiators. A Persian jumped down from a mantel and followed us until we reached the kitchen. Miss LaBarge turned on the overhead lightbulb, which bathed her in a dingy yellow glow.

There she was: her plain brown hair, small nose, and ruddy cheeks that made her look like a farm girl. Leaning on the back of a chair, she opened her mouth to say something, but then changed her mind and walked to the stove.

Arrested at the sight of her in the light, I shuddered, my entire body growing cold. Something wasn't right.

This woman looked exactly like Miss LaBarge, but at the same time she didn't. Her features were the same, yes, but the angles weren't correct. Her cheekbones looked a little higher; her jawline looked a little heavier; the wrinkles around her eyes looked a little less defined, as if she were a grainy photocopy of the real Annette.

She removed the lid from a dented kettle, crossed to the sink, and filled the kettle under the faucet. "Tea?"

I must have been staring, because Noah nudged me with his elbow.

"Yes, thanks," I said.

Miss LaBarge moved too briskly about the room. I watched, horrified, as she sliced a lemon and squeezed its juice into her tea. Miss LaBarge always preferred cream.

"You're-you're not Miss LaBarge at all."

The impostor put down the lemon and gave me a sad sort of look, like she pitied me. Wiping her hands on a dish towel, she pulled out two chairs at a plain wooden table. "Please, sit down."

Noah sat down at the end of the table, but I didn't move. I couldn't. I felt paralyzed and confused and angry, so angry. Who was this woman pretending to be Miss LaBarge?

Setting two mugs of tea on the table for us, she took a seat across from Noah. "My name is Collette LaBarge," she said. "I'm Annette's younger sister."

I nearly spilled my tea. "What?"

"Annette is dead. She died in August. I'm her younger sister."

All at once, everything suddenly made sense. I hadn't been seeing Miss LaBarge this year; I had been seeing her sister. It seemed too easy and too dreary to be true.

She frowned. "You look disappointed."

"I thought-"

"You thought she was still alive. You wish I were someone else." Collette's eyes had a coldness to them, and her hands were balled into fists, as if she were ready to fight. She leaned back in her chair. "I'm sorry."

"So there's no way she's still alive?" I uttered, only realizing then that somewhere within me I had reserved the smallest hope that Miss LaBarge had survived.

Collette lowered her eyes. "No."

"But then why are you here?" I asked. "Why are you in hiding? No one knows about you. You didn't even come to her funeral."

"I did attend."

"I saw you, then," I said, realizing that it was Collette on the coast that day as we sailed away. "But you weren't on the boat. You were on the sh.o.r.e."

"Annette and I weren't close."

I shook my head, trying to understand. "But every time I saw you on the street you acted like you didn't want to be seen."

She put down her mug. "When have you seen me?"

"The first time was at Miss LaBarge's burial. The second time was when your car stopped at an intersection. I wanted to talk to you, but you vanished. The third time, I was with Noah at a bakery in the old port, when you walked by. We followed you downtown, where you took an elevator into the underground. When we made it to the tunnels, we couldn't find you anywhere."

Collette didn't say anything for a long time, her eyes darting between us. Finally, she spoke. "Why have you come here?"

Noah's eyes met mine, but neither of us answered.

"Was someone chasing you?" she said, her eyes wild.

"We were looking for the secret of the Nine Sisters," I said finally.

Collette coughed.

"You know it?" I said, studying the way her eyes widened, the way she shifted her weight.

"You're asking a dangerous question," she said softly. "Looking for the secret of the Nine Sisters can only bring death-just like your parents', my sister's, Cindy Bell's. Or you'll become like me, living in confinement, waiting for the Liberum."

"It's too late," I said. "They already found us."

As my words sank in, a flicker of understanding pa.s.sed over her face. Her body grew tense as her eyes moving from us to the window. "Did they follow you here?"

"What do you know?" I said.

"Did you bring them here?" she said, growing panicked.

"It's possible," I admitted. "Please, tell us what you know. There isn't much time."

She pushed her tea across the table and gave me a level look. "I'll show you."

We followed her down a corridor and one set of stairs, until we were in an old cellar.

"We all became friends at Gottfried-your mother, Annette, Cindy, me. That's where we first heard about Les Neuf Soeurs. Like everyone else, at first we were just intrigued, but as we did more research, we started to believe that the secret still existed, hidden by the mysterious ninth sister. And what started as a hobby turned into an obsession.

"We traveled all over Europe-France, Italy, England -looking for any kind of information that might identify her. We searched through all of the French Monitor archives, looking for a talented girl of seventeen who had lived around the time of the Nine Sisters. Of course we didn't find anything. The problem was that we had focused our entire search on France, since that's where the Nine Sisters had come from. It never even crossed our minds to look in Montreal, where they sent their youngest member for schooling."

Collette walked to a hutch in the corner of the cellar. She opened one of the drawers and took out what looked like a box of loose leaf tea. Lifting the lid, she removed an envelope, yellowed with time.

"Annette gave this to me before she was killed. She said your parents had given it to her, and that it was incredibly important I keep it safe."

With that, she handed it to me. The paper was so worn it was almost transparent. It was addressed to Alma Alphonse in France. I remembered the name from Madame Gout's lecture: Alma was one of the eight sisters who was murdered. Gently, I opened the envelope and removed the paper, flattening it on the counter. It was faded and creased and smudged with oil, as if it had been folded and unfolded dozens of times. The right-hand corner was embossed with the crest of a canary.

April 2, 1732 Cher Alma, I fear we have made a grave mistake with Ophelia. Her doctor at the Saint-Laurent says she is responding well to treatment; however, after visiting her in Montreal, I am quite worried. She seems rash and unable to control her urges. In confidence, she confessed to me that she often desires to kiss people, and her mood fluctuates between rapture and severe melancholy, in which she complains of the world clouding to tedium. She is resistant to the treatment we give to her kind, and speaks of suffering from a moral crisis and lovesickness, though it is unclear with whom she is in love. The only person she seems fond of is her doctor, Bertrand Gottfried.

She has taken an unusual fancy to water. Her nurses say she studies it day and night, staring at the basin in her room or sitting by the fountain, a practice which is in stark contrast to the vigor and discipline she held as first rank Monitor. No doubt this is a reaction to the fire; however, I have asked them to remove her from St. Clement for the safety of the other students. Doctor Gottfried expressed interest in taking her to the American colonies, where he plans on opening a new hospital for the Undead, though I wonder if it will help. I implore you to consider the safety of our discovery. Ophelia Hart has changed too much. We cannot trust her, and I beg of you to consider the option of putting her to rest.

Votre Soeur, Prudence Beaufort I looked at Noah. "Ophelia Hart was a student at St. Clement when she was in a terrible fire?" I said, my mind racing as I scanned the letter once more. The world clouding to tedium. She often desires to kiss people. Unable to control her urges. Reaction to the fire. Those could only mean one thing. "She became Undead?" I said in disbelief. "Is that why she used the secret and then preserved it?"

Collette gave me a slight nod. "I think so. Your parents were the ones who first discovered that Ophelia Hart was the ninth sister. Your mother found this letter buried beneath a birdbath in Alma's old house. They retraced Ophelia's life and found the second part of the riddle in the hospital, in the same room where she first reanimated as an Undead."

"She must have planted it when she worked as the head nurse there one hundred years later," Noah said, his eyes trained on mine.

"And then she created the headstone," I said. "She must have erected it in honor of her teenage life. She etched the last part of the riddle on it."

Noah nodded, his expression almost sad.

My hands trembled as I held the letter, imagining my parents holding the exact same sheet of paper, just two years ago. "And Miss LaBarge and Cindy continued the search, a.s.suming the next riddles were hidden somewhere having to do with her research on water," I murmured. "That's why they were found near lakes."

Collette nodded. "I'm the only one of us left. I've been finishing their search but still haven't found the last part of the riddle."

Ophelia Hart had gone to St. Clement, just like me, and at some point while she was there, she had died. What could be more meaningful than that? "But they were wrong," I said. "The part of the riddle we're missing is the first part, not the last. And before Ophelia was a scientist, before she was a nurse, she was a student at St. Clement. She might have even died there." I turned to Noah. "Didn't your father say that she'd worked briefly as a nurse there?"

Too surprised to speak, Noah gave me a slight nod.

"What if she went back to work at St. Clement because she wanted to plant something there?" I said.

"The beginning of a riddle," Noah said, completing my thought.

And together, we turned to Collette. "We need to go back to school."

WE FOLDED OURSELVES INTO THE BACKSEAT of Collette's car and waited beneath a blanket as she drove us back to school. "I think it's safe," Collette said, turning the ignition off. She had parked in an alley a few blocks away from the entrance.

I closed my eyes, feeling for the vacant presence of the Undead. "They're close," I said. "But not here."

Noah and I slipped out of the car and down the alleyway, giving Collette one last nod before we disappeared into St. Clement.

The buildings surrounding the courtyard blinked with lights, turning on in one window, going off in another. We knew the first part of the message had to be in one of them, but we weren't sure where. The school was huge, with oddly shaped rooms and an endless maze of narrow hallways and dark crevices. It could be anywhere.

"Where would she have hidden it?" Noah said as we stopped in the shadow of a building.

In my pocket, I could feel the letter Collette had given me. Ophelia had left her home to go to school at St. Clement. She'd been sent here with a secret, just like I had been.

So if I were Ophelia Hart, where would I have hidden the first piece of the riddle? It had to be a place that was private, where no one would find me while I hid the clue; but it couldn't be too private, or else I risked the chance that no one would ever find it again. Most important, though, I would only bury my deepest secret in a place that had personal meaning to me when I attended St. Clement.

Suddenly I stopped walking, tripping Noah, who was a step behind me. "Her room," I said, as he pulled himself together. "It's in her old dorm room."

We went to the library. There, we rifled through the card catalog until we found the location of St. Clement's old school files. It was upstairs on the fourth balcony in a dim, dusty corner that looked like it hadn't been visited in decades.

I started from the right side, Noah started from the left, and, moving toward each other, we scanned the books, looking for a volume that contained all of the old housing a.s.signments. Each book was at least an inch thick, full of bound school doc.u.ments, and most were poorly labeled. I was about halfway through the top row when Noah called out to me.