Massachusetts, 1945

Grace Cahill held the two envelopes in her hand: one beige, one light blue. She stared at them for a moment before crumpling the blue envelope into a ball and tossing it into the crackling fireplace — the one redeeming feature of the dreary senior common room at Miss Harper’s School for Girls. It didn’t matter that the blue letter had been sent all the way from Paris. She was done with all that.

That Grace Cahill didn’t exist anymore.

All she cared about was the second envelope, which bore a US Army stamp and a label that read Passed by Army Examiner. Grace had received a few similar envelopes ever since her favorite teacher, Mr. Blythe, or rather, Captain Blythe, had joined the army. Although an old football injury had left him unfit for normal military service, the government had made an exception when they recruited for some top secret project involving stolen works of art. And so, three years after the United States entered the Second World War, Mr. Blythe resigned from his art history post and shipped overseas.

Grace slid her finger under the seal and carefully opened the envelope. The letter inside was scribbled on very thin stationery, and there were all sorts of stains and fingerprints around the edges from the censor assigned to screen it for security breaches. Grace trembled as she ran her finger over the wrinkled paper. It almost seemed to have battle scars of its own.

Grace grasped the arm of the couch as the room began to spin. She tried to force herself to breathe, but her chest seemed to be tightening, collapsing the space between her rib cage and her heart.

It wasn’t just the shock of seeing Mr. Blythe’s distinct handwriting. It wasn’t fear that the army was unearthing her family’s deepest secrets.

It was because Mr. Blythe was dead.

Grace leaned back against the couch, oblivious to the metal springs jabbing her spine.

Three weeks ago, during morning convocation, the headmistress had made the grave announcement. “I regret to inform you,” she’d said stiffly, “that Mr. Blythe was killed in action during a secret operation in Germany.” She placed the emphasis on odd words, like an actor reading a script for the first time, and for a moment, the meaning hung in the air. But then the chapel filled with the wails of girls — some genuinely distraught, some exaggerating their grief for the young, well-liked teacher.

Unlike the other faculty members at Miss Harper’s School, who doubted whether girls really needed to know much more than etiquette and dancing, Mr. Blythe had considered it his job to challenge his students. He’d taken a special interest in Grace and told her she was destined for “great things.”

He had no idea.

By the time she’d met Mr. Blythe, Grace had already flown a plane into the middle of a battle. She’d even found one of the 39 Clues that her family — some of the most powerful people in history — had spent centuries looking for.

It’d been easy to risk her life when she thought she was protecting the Clues from the power-hungry Cahill branches, or the mysterious Vespers. But over the past year, as news from Europe came streaming in through somber radio reports, chilling newspaper photos, and casualty lists, an unsettling realization began to fray the edges of her fantasy. The Cahills weren’t saving the world — they were going on an insane treasure hunt while the world burned around them.

This was why Grace had been ignoring the blue envelopes. They were from a Cahill at the Louvre museum in Paris, who wanted Grace’s help tracking down a painting — something to do with the Clues, no doubt. A year ago, she would have been intrigued by the challenge, but now the thought made her ill. She could only imagine the ways her more ruthless relatives had found to exploit a war that had already claimed millions of lives.

She glanced down at the letter and felt her stomach twist.

And now one more.

Grace ran her finger over the paper. Mr. Blythe must have written it a few days before he died. The envelope had traversed the war-ravaged landscape, avoiding bombs and bullets, in order to find its way to her.

It had survived, while the man who had written it had not.

She folded it in half carefully and tucked it into her bag. The war might not have stopped the Cahills, but they would have to carry on without her.

She was done.

By the time she arrived at the lecture hall, everyone else was seated. Grace had just slid into a seat by the door when Miss Harper, the headmistress, swept inside, followed by a woman she’d never seen before.

There was a faint rustling as the students hurried to straighten their papers, smooth their hair, and readjust their skirts so the hems draped gracefully over their knees. The headmistress cleared her throat. “Mrs. Prentice has taken ill and will be unable to teach for the rest of the semester.”

That was odd. Just yesterday, Grace had walked past the faculty lounge and caught a glimpse of the sprightly Mrs. Prentice showing the chemistry teacher how to foxtrot. She certainly hadn’t seemed ill then.

“Fortunately, we were able to find a wonderful substitute, Mademoiselle Hubert.” The headmistress pronounced the name “Oo-bear,” contorting her mouth as if forcing her reluctant lips to wrap around the foreign-sounding syllables. “She recently arrived from Paris to study . . .” She glanced at Mlle Hubert.

“Nineteenth-century American painting,” the other woman said, her French accent coating the words like a glossy veneer. “I spend most of my time in Boston, but I am happy for the chance to teach a few days a week.”

Grace had trouble believing that Mlle Hubert harbored a deep desire to teach. With her sleek bobbed hair, dark red lips, and elegantly tailored suit, she looked like she should be posing for a photographer in front of the Eiffel Tower instead of locked in a musty classroom, trying in vain to convince Mary Atkinson that Monet and Manet were two different people.

However, that wasn’t the only reason Grace had trouble taking her eyes off Mlle Hubert. She looked vaguely familiar, yet Grace couldn’t remember where she’d seen her. Perhaps their paths had crossed at one of the Boston museums. Over the past few years, she’d spent a good deal of her free time wandering around the Museum of Fine Arts. She’d even taken her little brother, Fiske, with her a few times. Although he’d never get to meet their mother, Grace could show him the paintings that had meant so much to Edith. Grace knew it was silly, but it was a comfort to drink in the same images her mother had loved.

“Lovely,” the headmistress said quickly. She clasped her hands and smiled at the class. “I suppose that’s all. Be good for Mlle Hubert, girls,” she said as she headed toward the door.

“Well then,” Mlle Hubert said, addressing the students. She smiled, and the corners of her ruby lips spread across her pale cheeks like a ribbon of blood. “Today, we discuss the Northern European Renaissance.”

Arlene Swenson, a nervous-looking girl with shortly cropped curly hair, raised her hand. Mlle Hubert nodded at her. “Yes?”

“We’ve been studying the Impressionists, miss —” Mlle Hubert raised her eyebrow. “I mean, mademoiselle.”

“Bah. I cannot stand zee Impressionists.” Mlle Hubert waved her hand dismissively. “All those silly dots.” She took a breath. “Non. The Renaissance painters were the real masters. I show you.” She sauntered over to the wall, switched off the lights, and slipped a slide into the projector. An image of a dour-looking man in a floppy black hat flashed onto the screen at the front of the classroom. “Voilà. Here we have very important work . . . erm, ‘Man in Hat.’ ”

Arlene cleared her throat. “Excuse me, mademoiselle, but isn’t that Rembrandt’s self-portrait?”

“Ah, yes, that is the more . . . colloquial title.”

She switched slides and a new painting appeared — a richly colored Madonna and child. “And another . . . very famous . . . masterpiece. ‘Lady in Long Dress.’ ”

“Hold on. Isn’t that —”

Mlle Hubert changed the slide before Arlene had a chance to speak.

“Wait!” Isabel Faust called out. “Can you go back? I didn’t get to finish my notes.”

“No time,” Mlle Hubert said brusquely. “We have much to do.” The next slide appeared, a chilling depiction of Christ’s crucifixion. “How charming.” She clicked through the next four paintings so quickly Grace didn’t have time to register what they were.

“Ah, here we are,” Mlle Hubert said, as a new image filled the screen.

Grace inhaled sharply as a flood of long-forgotten memories swept through her. It was “The Adoration of the Mystic Lamb,” Jan van Eyck’s masterpiece, and her mother’s favorite work of art.

“Sadly, the altarpiece disappeared a few years after the start of the war.” Mlle Hubert’s voice pulled Grace back from her thoughts.

“How can something that size disappear?” Arlene asked, a hint of skepticism coloring her tone.

“It is a tragic story.” The teacher sighed dramatically. “After the war began, the altarpiece was brought from Belgium to France for safekeeping. The director of the Louvre had arranged for important pieces to be hidden throughout the country, away from the fighting. But the ‘Lamb’ was seized by the Germans and has not been seen since.”

Although the crowded classroom was stuffy and warm, a chill passed over Grace. It was like hearing someone had died. She knew it was silly — the people in the paintings weren’t alive. They didn’t care whether they stood in the sun-drenched cathedral or in the dank basement of some Nazi art thief.

The altarpiece was another casualty of war, just like Mr. Blythe.

Grace tried to put it out of her mind, but an idea had formed that she couldn’t uproot.

The altarpiece had been in the Louvre’s care when it went missing. The woman writing her from Paris — Rose Valland — worked for the Louvre. Could that be what she wanted Grace to find? She instinctively reached into her bag to run her fingers along the edge of Mr. Blythe’s letter. His section was in charge of tracking down missing works of art. A wave of nausea passed over her. Had he been looking for the “Lamb” as well?

Grace held on to the edge of the desk as the room began to spin. For centuries, the Cahills had been using the military for their own purposes. Napoleon sent the French army to invade Egypt to help him find a lost Clue. What if Mr. Blythe’s department had been set up by Cahills searching for the altarpiece?

We could be the ones who sent him into danger.

We killed him.

“Ahem.” She looked up and saw Mlle Hubert staring at her.

Grace swallowed, trying to suppress the bile rising up from her stomach. “Can you repeat the question?”

The teacher pursed her red lips. “I was explaining that Van Eyck hid a number of messages in the work, and I was hoping that you would be so kind as to locate one on the slide.”

The other girls all turned to stare at Grace, but her eyes were automatically drawn toward one of the figures in the background. She knew that there were Hebrew letters painted onto the band of his hat, but something about Mlle Hubert’s expression made her hesitant to mention it aloud.

“I’m not sure . . . sorry.”

A flash of irritation crossed Mlle Hubert’s face. “You look at one of the most beautiful, complex works of art in the world and think nothing? C’est dommage.” Mlle Hubert shook her head. “Perhaps you are more interested in whatever is in your bag?”

Grace glanced down and saw that her hand was still inside her satchel. She snatched it back and placed both hands in her lap. “No, mademoiselle.”

The teacher took a step forward and extended her smooth, slender arm. “Give it to me.”

“It’s nothing.”

“I am not going to ask you again.”

Grace reached into her bag and removed the envelope, the sweat from her palm seeping into the paper.

The clack of Mlle Hubert’s high heels echoed through the room as she strode toward Grace and snatched the letter out of her hand. “From a boy, I assume?” She smirked. “It is best that I take it. You obviously cannot afford to be distracted from your studies.”

As Mlle Hubert sauntered back toward the projector, Grace felt a fresh wave of grief pass over her. But then her pain hardened into anger. She might not have been able to save Mr. Blythe, but she could certainly save his last letter.

Mlle Oo­-bear had no idea who she was dealing with.

Grace hit the ground silently. It had been six months since she’d gone for a midnight training run — six months since she’d resolved that her days as a Madrigal agent were over. But she hadn’t lost her knack for balancing on the sill, leaping for the tree branch, and then dropping lightly onto the spongy grass below.

She wasn’t going to allow Mr. Blythe’s last letter to molder away like some forgotten prisoner.

She was going to get it back.

Grace jogged across the lawn toward the back gate, passing Kendrick Hall, the ivy-covered building that housed the teachers’ offices. A light on the second floor caught her eye and a dark figure passed in front of the glowing window. Grace recognized the elegant silhouette.

It was Mlle Hubert.

Grace ducked behind a tree.

The window went dark, and Grace exhaled with relief. A minute later, a figure emerged from the building and hurried down the path, away from Grace.

When Mlle Hubert disappeared from sight, Grace darted out from behind the tree and ran up to the front door of Kendrick Hall. She turned the handle. It was locked. With a quick glance over her shoulder, Grace dashed around to the side of the building. She stood there for a moment with her back pressed up against cold brick.

She surveyed the lawn one more time, then turned around. The large bricks were old and uneven, which made it easy to find a foothold and hoist herself off the ground. Grace reached up, feeling the bricks for more cracks, and pulled herself even higher. A gust of wind rushed by, twisting the hem of her dress around her calves. Grace tightened her grip and shook her legs free one at a time. After flying an airplane into the middle of a raging battle and dodging bullets in the Tower of London, sneaking into a second-floor office was a piece of cake.

Grace rested her knee on the windowsill, braced one arm against the wall, and pulled up on the sash. It was unlocked. She lowered herself onto the floor, wrinkling her nose. Mlle Hubert had only been here one day, and already the room had changed. Mrs. Prentice’s office had always smelled like coffee and gingersnaps, but now the still air was saturated with the scent of perfume and cigarettes.

The room was dark, but the dim moonlight that filtered through the glass provided just enough illumination to poke around. Grace crept over toward the desk, scanning the jumble of papers, books, ashtrays, and teacups with red lipstick stains on the rims, but the envelope was nowhere to be seen.

A noise from downstairs sent Grace diving under the desk. She couldn’t afford to be caught breaking into a teacher’s office. Her father had warned her that she was one suspension away from being sent to live with distant relatives in Siberia. Not that the school would even be able to get hold of James Cahill if they caught her. Last she heard, he was in Brazil. Or was it Finland?

Grace tucked her legs in and braced for the sound of approaching footsteps. But none came. Sighing, she leaned back against the table leg and winced as something dug into the space between her shoulder blades. Grace twisted around and saw a raised seam running partway down the leg of the desk, as if a section had been replaced. She ran her finger along the edge, feeling it wiggle slightly, then dug her nails under the seam and pulled. A chunk of wood slid out, revealing a cylinder of tightly rolled paper.

Grace crept out from under the desk to where there was slightly more light, ignoring the thud of her heart against her chest. Had Mrs. Prentice done this? Or had her replacement been redecorating?

She removed the top paper and spread it out on the floor, holding the edges down to keep it flat.

It was a telegram sent from Berlin to Paris, dated a few weeks back. But it wasn’t written in any language she recognized. Certainly not German or French. She lowered her head for a closer look. The letters were all familiar — it was just the order that didn’t make sense. It almost looked like a code, but what sort of art history teacher was in the habit of hiding encrypted messages?

She ignored the prickle of fear in her stomach. There was no reason to jump to conclusions.

Not until she cracked the code.

Grace stood up and rummaged through the desk clutter for a pencil and a piece of paper. The message looked like it could be a substitution cipher, and since the letter V showed up a number of times on its own, that meant it probably stood for either I or A. If V stood for I, then it made sense that W would stand for J and so on. She started to scribble, her brow furrowing as a stream of nonsense appeared. She crossed it out and tried again, this time, with V standing in for A.

This time, the words looked familiar. The message was written in French! Grace knew the language well enough to translate.

Grace stared at her hastily transcribed message. If she waited long enough, perhaps the letters would rearrange themselves into words that made sense, that didn’t make her feel like she was free-falling.

The Vespers had the altarpiece. They knew she was being recruited to rescue it. And so they’d sent one of their agents to kill her.

It was one thing to fight for her life on a mission, when she’d knowingly rushed headlong into danger. But here? At school? She grabbed on to the desk to steady herself as her knees began to tremble.

Grace stuffed the telegram into her pocket and turned back toward the window. She tried to hurry, but her legs felt like they were made of lead. She took a deep breath, coughing as a cloud of French perfume filled her lungs.

“Good evening.” Grace spun around quickly, and slipped on the edge of the thin carpet, landing with a hard thud on the floor. She rolled over and looked up.

Mlle Hubert was leaning against the door, one hand resting casually on her hip.

The other holding a knife.

“I cannot decide whether you are much more intelligent than I supposed, or just much — what is the word? — more nose? Nosier.” She was looking at Grace with a combination of fascination and disgust. “But of course, that is what you Madrigals do.”

Grace rose shakily to her feet, cursing herself for not making it to the window in time. This is what happened when you stopped training. “So you’re here to kill me?” Grace asked, forcing her voice to assume a slightly condescending tone. She gave Mlle Hubert the same smile she’d seen her cousin Princess Elizabeth give young men who tried to impress her at royal gatherings. “They’ll find out. And I think you’ll find the éclairs in federal prison aren’t quite up to your standard.”

Mlle Hubert snorted. “That will not be a problem.” She held the knife up in the air so it glinted faintly in the moonlight. “Disposing of the body is the easy part.” She tilted the weapon to the side, as if it were a bracelet she was considering in a shop. “But that might not be necessary, if you decide to be cooperative.” She turned to Grace. “What do you know about the Ghent altarpiece?”

“Nothing,” she said quickly.

Mlle Hubert raised an eyebrow. “Then why was that teacher writing to you about it?”

Grace’s stomach twisted at the thought of the vile woman reading her letter, but she kept her face impassive. “He didn’t say anything about the altarpiece.”

“The actual name was censored, of course,” Mlle Hubert said, rolling her eyes. “But I know that is the work he was referring to. That is what he was sent to Germany to find.” She smirked. “That is why we had to kill him.”

Grace felt her heart speed up. “The Germans killed him.”

“The order came from a Vesper officer.”

“You’re working with the Nazis?” Grace spat.

Mlle Hubert smiled. “They are very good at carrying out orders. I think it only took one bullet to kill poor Mr. Blythe.”

It was as if someone had ignited a set of rockets attached to Grace’s feet. She launched herself at Mlle Hubert, wrestling her to the floor. She rolled on top of her and was about to deliver another blow when she felt something cold and sharp pressed against her neck. Grace lowered her eyes slowly. Mlle Hubert had the point of the knife digging into her throat. “Get up,” she said icily.

Grace hesitated, and her body grew rigid. She considered trying to knock the knife out of Mlle Hubert’s hand but, as she tensed her shoulder to make her move, the blade went deeper. Grace yelped.

“Quiet!” Mlle Hubert hissed. “Get up, now.”

She rose shakily to her feet and took a few steps back toward the door, but Mlle Hubert had risen quickly and was already standing in front of her, pressing the edge of the knife against the side of Grace’s neck.

“I am only going to ask you once more. What do you know about the altarpiece?”

Grace’s mind began to race as she desperately tried to recall everything her mother had told her about the “Lamb.” “There are hidden Hebrew letters on one of the figures’ hats,” she said quickly, feeling the blade rise and fall as she spoke.

Mlle Hubert pressed the knife deeper. “Everyone knows that.”

Grace’s heart was pounding, urging her brain to work faster. “One of the panels is a reproduction.”

“I know. We stole the original.” She pushed on the blade even harder.

“Van Eyck was a secret agent!” Grace gagged, fighting to speak as the knife pressed against her windpipe. That was something she remembered her mother telling her. “He was sent . . . by the Duke of Burgundy . . . to spy on other courts.”

“Yes,” Mlle Hubert snapped. “Which is why we want to know what secret information he hid in the paintings.” She lowered the knife and stepped to the side.

Grace gasped and brought her hand to her neck, wiping away the blood that had begun to trickle down toward her collar.

“I am done wasting my time,” Mlle Hubert said. “Max!” she shouted. A figure appeared in the doorway. An enormous man wearing a long coat . . . and holding a gun.

“Miss Cahill is not in the mood for conversation. Let us make sure she never has to make small talk again.”

The man raised his arm so the barrel of the gun pointed right between Grace’s eyes.

Grace leaped to the side the same moment the gun exploded. A bullet ricocheted off the wall next to Grace’s left ear, filling her head with a nauseating ring. She hurtled toward the window, and hoisted herself onto the ledge. There was another crack as a bullet hit the panes, showering Grace with tiny shards of broken glass. There was no time to climb down. She’d have to jump.

Grace twisted around so her feet were pointed toward the ground, took a quick breath, and let go, her arms flailing as she grasped at the empty night air.

She hit the ground with a thud and rolled a few feet. Everything hurt. But before she could assess the specific damage, the gunshots began again. Grace began crawling away from the building, shrieking as a bullet flew right past her cheek. The shooting stopped, and Grace knew that Mlle Hubert and the other Vesper were on their way downstairs. She had to get away. Grace rose to her feet, gasping as pain shot up her left leg.

“Help!” she screamed. “Somebody!”

She knew the dorms were too far away for anyone there to hear her, but there had to be someone around. A janitor. A teacher returning from a late night out. Anyone.

“Help!” she shouted again. But there was no answer. Her desperate scream was simply absorbed by the silence of the night.

She stumbled down the path toward the staff garage, gasping at the pain. Before she gave up training, she used to “borrow” the groundskeeper’s motorcycle for stomach-churning rides down twisty backcountry lanes. She prayed that it was still there.

She could hear footsteps behind her. Grace frantically grabbed the dead bolt and threw open the wooden doors. The garage was mostly empty, but she felt a wave of joy rush over her as she spotted the caretaker’s motorcycle leaning against the wall — just where she’d found it the last time she’d taken it.

Balancing on her uninjured right leg, Grace flung herself into the seat, stuck the key into the ignition, and kicked the motor over to start. The engine rumbled to life. She pressed the gas, shooting out of the garage like a rocket.

Mlle Hubert and her assassin were running down the path toward her.

“Kill her!” her teacher screamed, as Grace picked up speed.

The man raised his gun, but Grace leaned forward, hugging the motorcycle as the bullets flew over her back.

“The tires, you idiot,” Mlle Hubert shrieked. But it was too late. Grace sped past them, creating a rush of wind that blew Mlle Hubert’s scarf over her face. The front gate was open slightly. The Vesper must not have locked it when he sneaked into the school. Grace switched into a higher gear as she flew through the narrow gap and onto the road.

“Woo-hoo!” she shouted as she raced down the middle of the empty street, her hair streaming behind her.

It didn’t matter that, with every bump, her left ankle screamed in protest.

She was alive.

It was almost dawn by the time Grace coasted into the Boston Navy Yard. Set against the pink and orange sky, the enormous warships looked like they were emerging from another world. Grace shivered as she imagined them being forged by giants, sent to Earth to battle the evil that threatened to destroy it.

It had been foolish to ignore all those letters from the woman at the Louvre. No, not just foolish. Selfish. Reckless. And fatal. If she’d only acted earlier, perhaps she could have found the altarpiece. Mr. Blythe might have never been sent to Germany. He would never have been struck by a Vesper bullet.

It had been ridiculous to think that she could remove herself from the Clue hunt, separate herself from the Cahills’ centuries-old feud with a ruthless enemy. Growing up, she had always associated the word Vesper with evil, but it had been an abstract evil — like the villain in a fairy tale. Over the past few years, Grace, along with the rest of the world, had seen real evil. Or at least they’d heard about it, listening to seasoned radio announcers who couldn’t mask the horror in their voices as they reported on Nazi atrocities. They’d read about it, in newspaper articles about what soldiers discovered after they liberated the concentration camps.

A photograph of the prisoners flashed through her mind. The worn faces that looked like all life had been drained out of them, leaving hollow eyes and sunken cheeks like dry riverbeds after a drought. The thought of the perpetrators made Grace physically ill.

They were who the Vespers had chosen to do their dirty work?

She didn’t know what the Vespers wanted, but until they found it, innocent people would continue to die.

Unless the Cahills destroyed them first.

Commercial steam liners weren’t crossing the Atlantic. The only way to Europe was aboard a military ship or plane, and they didn’t sell tickets.

Grace knew what she had to do.

She leaned the motorcycle against a wall and covered it with a dirty tarp. Then, with a glance over her shoulder, she darted to the edge of a dock where navy workers were loading supplies onto one of the ships.

Grace slipped into the narrow space between the tall columns of crates and held on tight as the platform was hauled into the air.

A few minutes later, there was a loud bang, and everything went dark as the crate was loaded into what she assumed was the hull of the ship.

It was going to be a very, very long trip to France.

The first time Grace had crossed the Atlantic, it had been on a luxury ocean liner, where she’d spent the afternoons sipping tea in the parlor, and the evenings listening to a jazz trio play under a canopy of stars.

The stars probably hadn’t changed, but she was in no position to marvel at them.

Grace wasn’t even sure how long she spent in the cargo hold. There weren’t any windows, so she couldn’t keep track of the sunrises, and there wasn’t enough light for her to read her watch. For three or four days, she huddled on the cold floor, nibbling at the biscuits she’d unearthed from one of the crates, drinking from a fire hose she’d found coiled up in a corner.

If Beatrice could only see me now, she thought grimly, imagining what her snooty older sister would say about these accommodations. Beatrice would never stow away on a navy ship. She’d made it clear that she wanted nothing to do with their family’s secrets.

But Grace knew that was no longer an option for her. The Cahills had an obligation to do whatever they could to keep innocent people safe from the Vespers.

Her next stop would be the Louvre in Paris. She’d find out why that woman, Rose Valland, had needed her help, and what her plan was for retrieving the altarpiece.

She only hoped it wasn’t too late.

Grace awoke from her nap with a jolt as the crates rattled around her. In the distance, she could make out the sound of men shouting, and felt a current of excitement travel down her aching limbs. They had arrived in Normandy, in northern France.

Grace took a few shaky steps forward and peered around a stack of metal containers. She had to figure out how to get off the ship without being spotted. Even seventeen-year-old girls couldn’t get away with sneaking aboard a US Navy ship during wartime. She’d be lucky if she weren’t shot on sight.

She crept down a deserted corridor lined with small, round windows filled with hazy sky and blue-gray water. A strange mix of awe and sadness churned her stomach as she saw the ships scattered along the coast. It was the same beach the forces had landed on nearly a year ago on D-Day, the massive offensive that had allowed the Allies to gain control of crucial territory in northern France. She remembered the footage from the newsreels. The men storming up from the waves by the thousands, barreling into enemy fire. A staggering number of lives had been lost, but their sacrifice had not been in vain. The Germans had retreated.

Now it was Grace’s turn — to make sure Mr. Blythe’s sacrifice hadn’t been in vain.

She reached the end of the corridor and pressed her ear against a metal door. When she was sure no one was on the other side, Grace turned the handle and stepped into the light. She winced and held her hand up to her forehead to shield her eyes.

“Hey!” a man’s voice shouted.

Grace jumped like she’d been electrocuted.

“What in God’s name are you doing?”

Still half-blind, Grace spun around and started running.

“Come back here!”

Grace sprinted with all her might, but she was weak and woozy from her days in the cargo hold.

“Intruder!”

The thud of footsteps behind her exploded into a chorus of stomping feet and shouting voices.

Up ahead, there was a gap in the railing where a ramp met the deck. She took a sharp right and tore down the slippery incline.

“I got her!”

Grace felt fingers graze against her arm. She gasped and tried to pick up speed, but she had nothing left.

She was about halfway down the ramp, and the water loomed below her. Was it a twenty-foot drop? Thirty?

With her legs about to give out, Grace used her last ounce of strength to hurl herself over the railing. She forced her burning lungs to take one final gulp of air before her feet hit the water, and she plunged into the murky darkness.

Nine hours later, Grace was in the most beautiful city in the world, but neither the Eiffel Tower nor Notre Dame held any interest for her. All Grace could think about was how much her feet ached and how ridiculous she must look trudging across Paris in mud-splattered clothes that reeked of gasoline and salt water.

However, as she walked along the Seine toward the Louvre, Grace felt her black mood dissipating in the afternoon sunshine. She hadn’t been in Paris during the German occupation, but it was clear that the city was reveling in its freedom — delighting in its first spring since the liberation. The sound of children laughing danced down the cobble-stoned streets, young women in brightly colored clothes shot coquettish glances at the soldiers resting in the grass, and the sidewalk cafés buzzed with animated chatter.

It was hard to believe that, only a short time ago, German tanks had patrolled the streets and banners emblazoned with swastikas adorned many of the buildings. Paris was living proof that the tide of war had turned: The Germans were retreating.

Grace’s stomach rumbled as she passed a pâtisserie with a window full of pastel-colored macaroons, but now wasn’t the time to stop for a snack. As she crossed the Pont des Arts and the Louvre came into view, Grace forgot about her stomach. She’d been to Paris a number of times growing up, but was always astonished by the size, beauty, and grandeur of the magnificent Renaissance palace. Its three enormous wings surrounded a vast courtyard that Grace couldn’t look at without imagining it full of carriages and ladies with powdered wigs.

Grace dusted off her dirty skirt as best she could before marching into the entrance hall. She wasn’t in the ideal outfit for requesting an interview with one of the curators, but it would have to do. She raised her chin just like she’d seen her mother do before voicing her opinion to one of the many ambassadors who used to come to their house for dinner.

Grace walked toward the information desk, the clack of her shoes echoing throughout the nearly empty vestibule. The woman behind the desk was filing her nails. When she heard Grace enter, she set the emery board down and looked up in surprise, but her expression quickly transformed into disgust.

“Est-ce que je vous aide?” she said, wrinkling her nose.

Grace cleared her throat. “Bonjour. Je voudrais un rendez-vous avec Madame Valland.”

The receptionist stared at Grace as if she’d requested an audience with the president. “You are American, no?” Grace nodded. “Did you swim here?”

Grace raised her chin. “Yes. The North Atlantic is lovely this time of year. Especially now that the Germans have retreated. You’re welcome, by the way.”

The woman sniffed. “And what is your business with Madame Valland?”

“It’s private and confidential.”

“Well, you will have to make an appointment. Madame Valland is very busy.”

“I assure you, she’s been expecting me.”

The receptionist raised an eyebrow. “Rose Valland is the associate curator of the most famous museum in the world. She is far too busy to entertain American tourists . . . street urchins . . .” She waved her hand. “Whatever you are.”

Grace smiled benignly. “So busy that I imagine she doesn’t post her own letters.”

“I handle all of Madame Valland’s correspondence.”

“Then you are aware, no doubt, that she’s been writing to a Grace Cahill care of Miss Harper’s School in Massachusetts?”

She narrowed her eyes. “How do you know that?”

“I am Grace Cahill.”

The receptionist stared at her for a moment and stood up. “I see. In that case, I will show you to her office . . . mademoiselle.”

“Don’t bother. I wouldn’t want to take you away from what appear to be very important duties.”

The woman flushed. “Fourth floor. Take that staircase there.” She pointed.

Grace smiled. “Merci.”

Unlike the cheerful scenes she’d passed outside, the Louvre still bore the hallmarks of war. As Grace reached the fourth floor, she found herself in a corridor lined with ornate gold frames, the kind used to display the works of old masters like Raphael and Rembrandt. Except that the frames were empty. In place of canvases, their titles were scrawled in chalk on the walls. She shivered, overcome with a chill that had nothing to do with the drafts blowing through the cavernous galleries. It was like walking through a graveyard and recognizing the names on the tombstones.

She opened a small door that said ADMINISTRATION and entered a long hallway. Halfway down, she saw a door with the name VALLAND. It was open.

Grace paused. She’d been so focused on making it to Paris that she hadn’t thought about what she would say when she arrived. “Sorry I ignored all your letters”? “I couldn’t miss field hockey practice”? “I was convinced my family is evil but now I know the Vespers are worse so here I am”?

She took a deep breath and knocked on the door.

“Entrez,” a voice called.

Grace stepped inside the office. An older woman with dark, elegantly arranged hair was sitting behind an enormous claw-footed desk. Books and prints covered every surface. Tall stacks teetered precariously from the desk and chairs, and there were piles of documents scattered on the floor. Yet, despite the clutter, the office didn’t seem messy or disorganized. In her navy blue suit, the woman behind the desk radiated calm and authority.

Grace cleared her throat. “I’m Grace Cahill. I believe you’ve been expecting me.”

Rose Valland stared at her for what felt like a full minute, taking in Grace’s matted hair and stained clothes. Then her face broke out into a smile. “Well, this is a surprise.” She gestured to the one empty seat. “Please, sit down.” As Grace arranged herself in the threadbare armchair, Rose stood up to retrieve a tea tray balanced on the edge of a crowded end table and brought it over to the desk. “Tea?” Grace nodded and was handed a delicate white cup decorated with blue flowers.

“I’m sorry I didn’t write back,” Grace said. She clutched the teacup, savoring the warmth she felt seeping into her skin.

“I understand,” Rose said, taking a sip of tea and then returning the cup to the saucer. “The war has been difficult for all of us.” Grace tilted her head down, so Rose wouldn’t see the blush spreading over her cheeks. She’d spent most of the past few years safe and sound in America, far away from the fighting.

But she was here now.

She raised her chin. “I assume you want me to find the altarpiece.”

Rose looked startled. “How did you know? I didn’t mention the name in my letters. It was too dangerous.”

Rose’s face grew pale as Grace told her about Mr. Blythe and Mlle Hubert. “But why do they want the altarpiece?” Grace asked, taking a moment to sip her tea.

Rose walked over to one of the piles and picked up a large book resting on the top. She brought it over to the desk and sat back down in her chair. “Well,” she said, opening it to a spread featuring the Ghent altarpiece. “Scholars have always been fascinated by the elements that suggest Van Eyck traveled far beyond Europe.” She pointed to a cluster of palm trees so lifelike they looked as if they were about to begin swaying in the breeze. “How could a man who supposedly spent his whole life in Belgium paint palm trees without seeing them?”

Rose moved her finger over to a classical statue in the corner of another panel. “And this. It is almost a perfect reproduction of a Donatello piece in Italy. You have to remember that in Van Eyck’s day, books were extremely rare. It is not as if he could have seen a painting of Donatello’s sculpture. The incredible accuracy suggests that he went on journeys — trips he chose not to document.” She looked up at Grace. “The Vespers believe the panels conceal a map that leads to secret locations in all the places Van Eyck visited.”

“What are they looking for?”

“We’re not sure.” Her lips pressed together and her face turned serious. “But it’s something important enough they’re willing to kill for it.” She placed her hand on Grace’s shoulder. “Come with me.”

Grace followed Rose through the deserted galleries. As they passed countless empty picture frames, Rose explained that the Nazis had been seizing priceless works of art since the war began, but the altarpiece had held a particular fascination. “The ‘Lamb’ has been a symbol of many things for many people,” she said as they swept down a marble staircase. “Over the centuries, it has been claimed by rulers who saw it as a mark of prestige. Others — even non-Cahills — believed that it hides the key to a priceless treasure. Hitler is convinced one of the panels contains a map to the crown of thorns Christ wore during his crucifixion, which supposedly has supernatural powers.” She gave Grace a wry smile. “That’s probably why it was so easy for the Vespers to convince him to track it down.”

They turned into a cavernous sculpture gallery. In the dim light, the few remaining statues cast long shadows, making it look like the empty pedestals were haunted by the ghosts of their missing occupants.

“So we need to find the altarpiece before the Vespers decode the map?” Grace asked, running her hand along the top of an empty pedestal where, according to the chalk markings, a Greek statue of Athena once rested. “And I’m part of the rescue team?”

Rose shook her head. “Your friend Mr. Blythe’s division — the Monuments Men — think they’ve located the storehouse where the Germans have been hiding the stolen works of art.”

“So what do you need me for?” Grace said, her voice rising with frustration.

Rose ignored her tone and continued calmly. “The Germans are monitoring the Monuments Men. We believe they have orders to demolish the storehouse if the Allies get too close. They would rather destroy thousands of European masterpieces than hand over their stolen treasures.”

Grace narrowed her eyes. “How do you even know this?”

Rose walked over to a large ceramic urn. She glanced over her shoulder, grabbed on to the handle, and pulled.

Instead of the smash Grace expected, she heard the clank of twisting gears. The urn began to rotate, sinking down into the concrete pedestal until it disappeared completely, revealing an empty compartment. Rose reached in, pulled out a folder, and beckoned for Grace to stand next to her. She removed a stack of documents: letters and telegrams in a variety of languages.

Grace gasped as she glimpsed a black eagle clutching a swastika. “How did you get that?” she whispered.

Rose smiled. “Because, dear, I am not just a Madrigal. I’m also a member of the French Resistance.”

Grace wandered through the empty gallery in a daze. She couldn’t believe she’d agreed to this. Rose wanted her to stall the Nazis — to keep the altarpiece safe until the Monuments Men arrived. Because if the “Lamb” were destroyed before the Cahills decoded the map, they’d lose their one chance to discover what the Vespers were after.

Grace knew why saving the altarpiece was important, but the plan — if you could even call it that — was insane. In order to reach the “Lamb,” Grace would have to sneak into the heart of Nazi-occupied Europe. The thought of getting into Austria was sheer madness. Exploring Altaussee — the town Rose identified — was tantamount to a suicide mission.

Rose told Grace that she knew someone who might be willing to fly her to Austria — a contact from the French Resistance. Their code of secrecy prevented Rose from calling her while Grace was in the room, and she politely requested that she wait in the gallery.

The museum was so quiet that Grace could make out the sound of a radio broadcast coming from one of the nearby offices. The familiar cadences settled in her ear and sent a shiver down her spine. It was President Roosevelt — the late President Roosevelt, more accurately. He’d died only a few weeks ago, and the whole country was still in mourning. This French radio program seemed to be playing snippets from Roosevelt’s famous speeches. But this was something Grace hadn’t heard before: a speech about the missing art in Europe.

“Whatever these paintings may have been to men who looked at them generations back — today they are not only works of art. Today they are the symbols of the human spirit, symbols of the world the freedom of the human spirit has made.”

She shivered. The freedom of the human spirit.

Mr. Blythe hadn’t known anything about the altarpiece’s secrets, and had still been willing to risk his life to protect it. He’d known that art was worth fighting for.

It wasn’t about hidden Clues or secret maps. Being a Cahill meant using your power to stop whatever evil was threatening the freedom of the human spirit.

Whatever the Vespers were looking for, they couldn’t be allowed to find it. Someone had to save the altarpiece before it was too late.

She looked around the empty gallery.

And apparently, that someone was her.

Grace stared uneasily at the young woman next to her — a young woman who was piloting her in a battered, single-engine plane over the Austrian countryside. Being a Madrigal involved risks, but flying through German territory in a rickety plane was something else completely. It was a death wish.

Yet Jane Sperling — if that was even her real name — looked completely at ease as the tiny aircraft sputtered over eastern Switzerland.

Grace had a million questions for the mysterious girl. How did she know Rose? Why on earth would she be willing to take Grace to Austria? And what was her plan to keep them safe once they entered enemy airspace? Yet there was something about Jane’s smirk that kept Grace from voicing any of her concerns.

“Sooo . . .” Grace tried one more time to extract a shred of information. “You’re a friend of Rose’s?”

Jane smiled but kept her eyes focused straight ahead. “That’s right.”

“You were in the Resistance with her?”

She laughed, which made her look much younger. She was closer to Grace’s age than she’d realized. “If I were, do you think I would have lasted this long if I blabbed secrets to strangers?” Jane turned to look at Grace for the first time. “Rose said you speak German.”

“Yes . . . ja . . . a little. But not enough to hide the fact that I’m American.”

Jane turned back to the windshield. “That could be a problem.” Grace stiffened, prompting a derisive snort from Jane. “If you are scared already, you are going to be in real trouble.”

“If I weren’t scared I’d be insane,” Grace said, narrowing her eyes.

“And yet you’re risking your life to find the Ghent altarpiece.” She smiled. “You must be quite the art lover.”

“It’s a little bit more complicated than that,” Grace snapped.

They flew on in silence. Jane fiddled with the controls on the dashboard, and then sat up straighter. “We’ve crossed into Austria,” she said.

The plane sank beneath the cloud cover, and the countryside came into view. It looked like something off a postcard — sparkling turquoise lakes were tucked among emerald green fields dotted with tiny houses with peaked roofs.

“Are you going back to France?” Grace asked.

Jane shook her head. “I have business to attend to in Bavaria.” She turned to Grace. “That’s in Germany.”

“I know,” Grace snapped.

A rumbling in the distance shook Grace’s mind free of all thoughts except one. She gasped as a plane emerged from a bank of clouds, followed by two more. The wings each bore a black-and-white cross that she recognized from countless newsreels. Their tails bore large swastikas.

It was the Luftwaffe.

The German air force.

Without saying a word, Jane banked the plane sharply to the left, and Grace felt her stomach plummet to her toes. The German planes disappeared from view, but she could hear the buzz of their propellers close behind.

The green expanse of farmland was suddenly swept overhead as Jane took them into an inverted turn. Grace squeezed her eyes shut as the blood rushed to her head.

“Hang on!” Jane shouted as she leveled the plane and began picking up speed.

“Thank you for the warning!” Grace yelled, without opening her eyes. “I was just about to take a little nap.”

Jane laughed as she pulled the throttle back as far as it would go. The plane began to shake.

“Open your eyes. You’re missing the view.”

The snowcapped peaks of the Austrian Alps glittered in the distance.

“Ch-ch-charming,” Grace said, as the plane rattled violently. She clasped her hands over her stomach as a wave of nausea passed over her.

Grace yelped as the patter of gunfire pierced the roar of the engines. The plane rocked back and forth. She could hear the ping of bullets tearing into the wings.

Jane pushed the stick forward, sending the craft into a nosedive. They hurtled straight toward the ground. The farmhouses and trees below seemed to grow at an alarming speed. A scream burst out of Grace’s chest but got lodged in her throat.

At the last minute, Jane straightened the plane and they glided over the tops of pine trees rustling in the wind. “Are you okay?”

Grace forced herself to swallow. “Never better.”

Jane grinned as she turned in a large loop, skirting around the side of a steeply sloped mountain and entering a narrow valley. “We should be safe here. Those Luftwaffe planes are too large to maneuver through this pass.”

The gap between the mountains was so small the sunlight filtered through the thick pine trees, giving it a greenish tinge. Emerald shadows filled the windows of the plane, making it seem like they’d flown through a portal to another realm. An enchanted world untouched by war. Unscathed by the Cahills.

But it seemed to have its own monsters.

Up ahead, a dark shape was hurtling toward them at an incomprehensible speed.

“Looks like I was wrong,” Jane said, gritting her teeth. “There’s a first time for everything.”

In the past, dangerous situations had always made Grace feel more alive, giving her the energy to do whatever it took to survive. But now there was no escape. A strange numbness passed over her, as if her body was trying to get a head start on dying.

There was a rapid patter of gunfire as the approaching plane began shooting at them. Jane banked hard to the left until they were almost vertical, and then rotated one hundred eighty degrees in the opposite direction, swinging the plane back and forth like a pendulum.

The German plane was so close Grace could see the shape of the pilot through the windshield.

The only comforting thought was that, in less than ten seconds, he was going to be dead as well. Grace shut her eyes. She wanted to scream, but her throat wouldn’t let any sound out.

Then she was weightless, floating through the air. This must be what it feels like to die.

Her stomach plummeted, as if it had parachuted out of the plane on its own. She opened her eyes and saw that they were suddenly flying low to the ground. The other plane was nowhere in sight.

“Woo-hoo!” Jane hollered. She reached over and slapped Grace on the shoulder. “I knew he’d fly over us at the last minute. Those Nazis are all cowards, when you get down to it.”

They zoomed out of the valley and back into the sunlight, flying over a green meadow dotted with wildflowers.

“We’re close to Altaussee. I am going to land here, and then you can hike down the mountain. Okay?”

“Absolutely,” Grace said, regaining her breath. She pressed her nose to the window as she surveyed the area. There was no obvious military presence, but that didn’t mean they weren’t nearby. The Luftwaffe pilots had no doubt put the ground troops on high alert, and the German army would not take kindly to an American girl sneaking across their border. It wouldn’t even be “shoot first, ask questions later.” More like “shoot first, then throw the body in the lake.”

There was a bump as the wheels hit the ground. After a very short taxi, Jane cut the engine, reached over Grace, and opened the door.

Grace unhooked her safety harness and turned to the pilot. “Thanks for the ride.”

“Good luck. I hope to see you again someday, Grace.”

Grace gave her a nod and jumped down. She watched as Jane restarted the engine, turned the plane around, and took off down the makeshift runway. Then she was gone, leaving Grace alone in one of the most dangerous countries on Earth.

When she reached the road, Grace turned left. Rose had told her the warehouse was somewhere in town, but the exact location was unknown. She might as well head downhill and try to get her bearings. Or at least think about how to avoid getting killed.

As she skidded down the steep, wildflower-lined path, Grace had to keep reminding herself that she was in enemy territory. It didn’t matter that the houses all looked like they belonged in a cuckoo clock. The beautiful setting didn’t change the fact that Austria was under control of one of the most ruthless military regimes in modern history.

The rumble of an approaching car sent her flying for cover, ducking behind a crumbling stone wall. As it turned a corner, Grace sat up and peeked over the edge. It was just a truck full of vegetables. She sighed. Her progress would be pretty slow going if she hid every time someone passed.

As she approached the town, the houses grew closer together. A small boy was playing with a dog in front of one of them. Grace took a deep breath and squared her shoulders. Act like you belong, she told herself. “Guten Tag!” she called cheerfully. The boy just stared at her. Okay, so maybe Austrians aren’t supposed to be friendly. She just hoped she hadn’t aroused too much suspicion.

A group of boys turned a corner and began walking toward her. One of them smiled at Grace, tipped his hat, and addressed her in rapid, heavily accented German. She felt her heart speed up. If she answered, they’d know she wasn’t Austrian, and they might ask questions. Using her nerves to her advantage, she blushed and gave a shy smile. The boys laughed and continued on.

By the time Grace reached the village, her heart was thudding so loudly she was surprised the army hadn’t been called in to investigate the commotion. Unsure what to do, she sat on a bench and tried her best to look Austrian. Whatever that meant.

The clip-clop of hooves caught her attention and she looked up. A bony gray horse was pulling a large wagon covered with a tarp. Although the driver looked like a normal farmer, Grace gasped when she saw the three men walking beside the wagon.

With their long coats, shiny tall boots, and red armbands, there was no mistaking them. They were members of the SS — the most elite — and deadly — unit in Hitler’s army.

The SS had been one of the keys to Hitler’s rise to power. They arrested people in the middle of the night. They tortured anyone they thought had useful information. Anyone who posed a threat was taken into a dark alley and shot. It didn’t matter that Grace was only seventeen. That she was a girl. If she were caught, she’d been treated like a spy.

She’d be tortured.

Then killed.

“Alles in Ordnung, Fräulein?”

Grace looked up and found herself facing one of the officers. He had a curved scar that stretched from the corner of his mouth to the tip of his ear. His expression was inscrutable. He might have been commenting on the weather, or accusing her of treason.

“Ja,” she croaked, praying he’d only said “How are you?”

The officer stared at her for a moment. The he nodded, spun on his heel, and began marching back toward the wagon.

Grace half exhaled, half sobbed, burying her face in her sleeve. She had to get out of here. There was no way she was going to find the altarpiece. The only thing to do was try to escape with her life.

Grace looked up and saw the wagon turning a corner. The tarp didn’t stretch all the way down, allowing her a glimpse of the cargo. It was dynamite.

It was true. They were going to blow up the altarpiece.

If she was correct about the dynamite, then chances were that wagon was heading to the secret storehouse. This was her best shot.

Grace leaped to her feet and scurried after the wagon. When the SS officers were looking the other way, she lifted the tarp and scrambled underneath it.

She was a mouse diving headfirst into a snake pit.

A mouse delusional enough to think it could save the world.

This is the stupidest thing I’ve ever done, Grace admitted to herself as she rocked back and forth with the movement of the wagon, struggling to keep her balance while sitting on a pile of fused dynamite.

After climbing steadily for about twenty minutes, the wagon stopped. The officers began barking orders in German, and she heard the clomp of approaching boots. Grace tunneled deeper under the mound of explosives, praying that they weren’t planning on unloading it all at once. There was a flurry of shouting and activity, and Grace could feel the top layer of dynamite being carried off the wagon.

With every movement, the soldiers came closer to discovering her.

She didn’t think her heart could race any faster, but then she felt a breeze brush against the back of her calf and realized her leg was exposed.

A strange numbness passed over her, as if the faster her heart beat, the slower the rest of her body became. In just a moment, it would stop forever. She was sure of it.

Would it hurt? Or would the soldiers just shoot her in the head and be done with it? She braced against the bottom of the wagon, waiting for the crack of the gun followed by . . . whatever came after.

“Halt!” a voice rang out. The movement in the wagon stopped, and she heard the sound of footsteps growing fainter. Whoever had been unloading the wagon seemed to have moved away. Grace sat up slowly and crept to the edge. She took a breath and then peeked around the side.

To her surprise, she wasn’t in the town. She’d assumed the art would be hidden in a fortified villa, or perhaps a discreet-looking warehouse. But the wagon had stopped halfway up a steep hill, next to the entrance of some sort of cave, or perhaps a mine. There were soldiers rushing in and out, giving orders to the workers carrying stacks of dynamite inside.

She ducked back behind the wagon as two long lines of soldiers marched by in rigid formation. The clomp of their boots could have been used as a metronome. They weren’t wearing the elaborate uniforms of the SS officers, but they all had red armbands emblazoned with large black swastikas that made Grace’s stomach churn with revulsion.

Something was definitely going on. Grace was no military expert, but she knew that you didn’t send what looked like more than forty soldiers to guard a mine. Unless there was something important inside.

When the coast was clear, Grace darted from the wagon and dove behind a large rock next to the entrance. She caught her breath for a moment, and then peered around. Some of the dynamite was being loaded into metal trolleys whose tracks seemed to stretch down into the mine. If the altarpiece was somewhere inside, the trolley would probably take her there.

She watched the movement of soldiers and workers for a moment, waiting for a break in the flow. Her heartbeat was loud but had slowed considerably, as if it were counting down the moments before she made the riskiest move of her life.

Three . . . two . . . go! Grace launched out from behind the rock, took a few flying steps, and leaped into the trolley, landing with a clank that shuddered through her whole body. She heard an officer bark another round of orders, and suddenly, the trolley began to move. She was heading into the mine.

The light faded rapidly as she rolled down the tracks. For a moment, she was swallowed by complete darkness, but then the trolley swept around a bend and Grace found herself in a passage lit with flickering bulbs. She listened for the sound of footsteps or voices, but there was nothing but the buzz of electricity.

Grace rose to her knees, wincing as she rubbed her elbows. Apparently, being a Madrigal meant spending your whole life black-and-blue. But as Grace looked up, her grimace collapsed into a gasp. This wasn’t just a mine; it was a sophisticated storage facility. Metal shelves lined the stone walls, interspersed with heavy hooks.

But that wasn’t what took Grace’s breath away.

It was the paintings.

There were thousands of them hung in neat rows, stretching all the way down the passage until they disappeared into the darkness. Enormous oil paintings, smaller pastels, horizontal landscapes, and round portraits. She blinked, expecting the paintings to vanish, like the fragments of a dream fading in the sunlight. But there they were.

The trolley stopped and Grace climbed out. She glanced over her shoulder and dashed over to where a canvas tarp draped over a ladder. There were noises coming down the passageway, angry voices and stomping boots.

“What do you think you are doing?” a man whispered in English.

“Warum sprechen Sie auf Englisch?”

“I am speaking in English so that no one overhears me and panics,” the first man answered. Grace peered through a hole in the tarp and saw a tall officer with silvery hair gritting his teeth with frustration. “The Allies are coming. They are less than ten miles away.”

The other man, also wearing an officer’s uniform, stared at him in shock. “What are our orders?”

The first man scowled. “We stuff the mine with dynamite, and light the fuse.”

The second man glanced around, bewildered. “Without removing the art?”

“Ja,” the first officer spat. “Now go fetch your men. Schnell!” He spun on his heel and marched away. The second man muttered something in German and then followed.

Grace felt her knees buckle as she grasped on to the cold wall for balance. She probably had no more than five minutes to find the altarpiece. But then what? She didn’t even have a gun. How was she supposed to keep it safe until the Allies arrived?

She glanced around to make sure the coast was clear and then stepped out from behind the ladder. A light in the next passageway caught her eye — a faint sparkle in the darkness. She walked toward it, feeling the air grow cooler as she moved deeper into the mine.

It was the angel Gabriel’s wing, painted with exquisite gold leaf, glittering from an enormous painting.

It was the altarpiece.

She’d found it.

At first, she was simply mesmerized by the colors — vibrant hues she’d never even thought to imagine while looking at the black-and-white photos in her mother’s book. It was uncanny to see the faces she knew so well displayed on such a grand scale — like seeing a movie star walking down the street. Some of them looked so realistic that Grace had trouble focusing her gaze. It almost felt rude to stare.

Grace looked around. The altarpiece was in a cave of sorts off the main passage into the mine. She rapped her knuckles against the stone wall. It felt strong enough to withstand at least a small explosion. But would that be enough to keep the “Lamb” safe if the Nazis lit the fuse?

If there were a way to seal off the entrance to the cave, the altarpiece might survive a larger blast. She dashed out into the passage. The trolley was still there, full of dynamite. She grabbed an armful of sticks and ran back to the altarpiece, silently cursing the faculty at Miss Harper’s School for never teaching her anything useful.

Like explosives.

Ten minutes later, Grace stepped back to survey her handiwork. It was an admittedly shoddy job. Her Ekaterina cousin Bae Oh would certainly have laughed at her. But she’d wedged a stick of dynamite above the entrance to the cavern — far enough away to seal the entrance to the cave, but leave the walls, and the contents, intact.

If the explosion was too small, the guards would find her before she’d secured the “Lamb.” They’d kill her and then destroy the altarpiece.

If the explosion was too big, it would destroy the whole mine — killing her and everyone in it. All those workers she’d seen filing in and out. They weren’t Nazis — they were just men struggling to support their families in the only home they’d ever known.

Grace jumped as a shout rang through the mine. It was the officer. For all she knew, that could be his order for everyone to evacuate before they blew everything up.

There was no time to lose.

Grace pulled a matchbook out of her pocket and, with shaky fingers, extracted a match. She stared at it for a second before striking it against the stone wall. A tiny flame danced in the gloom. Grace took one last look at the altarpiece and whispered “Godspeed” before touching the match to the fuse.

For a moment, she felt like she was running in slow motion. Then there was a bone-shaking boom followed by a wave of heat. The force of the blast knocked Grace to the ground. She felt a jolt of pain in her wrist that was quickly overshadowed by a burning sensation in her foot.

She rolled onto her back, and saw that she was surrounded by thick black smoke.

Grace scrambled to her feet, shrieking as a flame scorched her calf and began traveling along the hem of her skirt. She beat it out with her hand, spun around, and began running for her life

She felt a wave of gravel and soot spray the back of her neck as she tore up the tracks. Halfway up, she found another empty trolley and dove inside, gasping for air as her body quaked from the effort. There was a chorus of shouts from above.

“Sie sind hier!” a voice screamed.

They’re here.

“Zerstören das Altarbild!”

Destroy the altarpiece!

Grace heard some quiet mumbling, followed by a screech that practically seared her eardrums.

“What do you mean, the cave is sealed?!”

She couldn’t contain the laugh that bubbled out of her. Grace turned and saw a soldier standing over the trolley, his gun raised directly over her head. And then everything went dark.

“Miss . . . miss . . . Are you okay?” a voice called from somewhere far away.

She sat up and was overcome by a wave of nausea. The world was a sea of wavy blue and green lines that refused to come into focus. “Lie back down,” the voice commanded as a large hand guided her head back to the ground. She blinked and saw someone standing over her. He was tall, and wearing a very dirty uniform.

“Who are you?” Grace croaked. Her mouth felt like it was full of ash.

“You’re American?” He lowered himself down to the ground and stared at her. “I’m Lieutenant Greene. What in God’s name are you doing in Austria?”

“Is the altarpiece okay?” she asked, trying to sit up. The Allies had obviously arrived, but what had happened to the “Lamb”?

“How do you know about that?” he asked, his eyes widening. “Who are you?”

Grace ignored the question. “I . . . I . . . ” She inhaled sharply. “I think I might’ve blown it up.” Just saying the words was enough to start her body shaking.

“Whoa! Calm down there.” Lieutenant Greene grabbed her shoulders. “It’s fine. We have a map of the storage facility — or whatever this thing is. The altarpiece was in its own cave that was somehow sealed off. It’s under some rubble, but our engineers think that it’s most likely intact.”

Grace sighed, lowered herself back to the ground, and closed her eyes.

“Just stay there,” she heard Lieutenant Greene say. “The medics are on their way. Don’t worry, we’ll get you back home safe.”

Safe.

The altarpiece hadn’t been destroyed. The Cahills still had a chance to learn what the Vespers were after and figure out a way to stop them.

Someday, the word safe would mean something again.

She took a deep breath, inhaling the scent of pine that punctuated the smoky air, and smiled. If you had to be lying half-unconscious somewhere, the Austrian Alps weren’t the worst place to be.

She had a feeling she was going to end up in much stranger places before this thing was over. She wasn’t going to hide from it any longer — the Clues or the fight against the Vespers.

The Vespers had been right to send Mlle Hubert after her. Grace was a threat.

And she was just getting started.