Prologue

November, 1949
Presidential train
En route to Grand Central Terminal, New York

Dr. Berger looked into the long dark mouth of the tunnel. This tunnel would lead to another and then another until they stopped at a secret platform under New York City's Waldorf Astoria hotel. Only one train had permission to stop there. This one—the presidential train car. It hadn't been used by the president since the war and, despite its original purpose, the car was surprisingly utilitarian—simple wooden cabinets, a stainless steel counter bearing four liquor decanters, and leather chairs bolted to the floor.

He clutched his precious briefcase with nervous fingers. The train had almost arrived at its destination, and nothing had gone wrong. Yet.

Darkness engulfed the train car as it pulled inside. The train slowed to a crawl. To see why, Dr. Berger adjusted his round spectacles and peered through bulletproof glass so thick that it had a green cast. Dim, electric lights hanging from the ceiling revealed a field of silver tracks merging together again and again as the tunnel narrowed. The engineer had slowed to switch tracks. The car was deep underneath the city now. Close.

He cast a sidelong glance at his sole traveling companion: the uniformed soldier who was tasked with protecting him and the secrets he carried. What did he know about the man?

What was there to know? The man sitting straight-backed and alert with a Thompson submachine gun flat across his lap was merely an ordinary American soldier. A soldier much like the one who'd taken Dr. Berger prisoner in Bavaria a few years before. Another square-jawed man with close-cropped hair whose narrow eyes told Dr. Berger how much he hated all Germans. Of course he did—because of the war. These American soldiers held him personally responsible for all the deaths caused by Hitler's madness, as if these soldiers could have influenced Roosevelt's decisions themselves, as if his adherence to orders was so different from theirs.

In the end, he had defied his superior's orders when he'd packed up his notes and gone to meet his destiny on a train not unlike this one, fleeing west, praying only to surrender to the Americans and not the Russians. He'd been lucky. The troops who'd stopped his train were sturdy and well-fed, chewers of gum and crackers of jokes—American through and through. Their orders regarding high-level scientists were clear, and they hadn't mistreated him.

They'd brought him to the United States, interrogated him respectfully, and paid him a good salary to continue his research. They'd even retrieved his yellow parakeet, Petey, and the upright piano he had inherited from his father. His specialized knowledge had put him in the president's own train car on a special and secret mission that would change the future.

Funny how things turned out.

"Near now," Dr. Berger said.

The soldier jerked his head. Almost a nod, but not quite. The man had probably been given instructions not to speak to him. As kind as they seemed, the doctor doubted his American colleagues trusted him. A mutual state. The wounds from the war had not had time to heal.

Dr. Berger's fingers tapped out a song on his briefcase, but instead of helping him play music, the notes in its leather interior helped him to play the human mind. The trials were promising indeed, though protocols in the United States were more complex than they had been in Germany. Here he spent too much of his time talking about safeguards, about how to minimize risk and wondering if his funding would be canceled.

He hadn't worried about such things in Germany.

The SS valued only results.

He tilted his head, certain that he had heard a familiar sound. The clacking of steel wheels against track filled his ears. The reassuring rhythm told him that every second brought them closer to their destination. He closed his eyes and relaxed.

The sound came again—like Petey's soft warble when he tapped his mirror with his rounded beak. This sound wasn't quite the same. Seeking its source, he scanned the front of the car. A small hand emerged from behind the door of a cupboard at the front of the car, and tiny brown fingers with dark nails groped the frame.

"Gott im Himmel!" The precious briefcase slid unnoticed to the floor as the doctor sprang to his feet and brushed past the startled soldier. The little hand vanished behind the wooden door as if it had never been there. But he had seen it.

Dr. Berger lurched toward the cupboard. It was impossible. It couldn't be there. It must not be there.

"Come out, little one." He eased the door to the side. Its nerves were probably on edge, too, and he had no wish to startle the creature.

The soldier stood behind him, gun trained on the half-open cupboard. "What's in there, doc?"

So, he could speak.

Dr. Berger reached inside the cabinet with one cautious hand while speaking in a gentle singsong voice. "No one will hurt you. We are all friends here."

Leathery fingers curled around his wrist, and a slight weight dropped onto his forearm. Slowly, he pulled the creature out.

"A monkey?" asked the soldier.

Not just any monkey. The animal on his arm was a female rhesus monkey. Short brown fur covered her plump body, except for the inverted pink triangle of her face. Huge brown eyes stared up into his.

"Do I know you?" Dr. Berger crooned.

He touched her soft ear and felt for a tag punched through the cartilage. His heart sped with fear, and the monkey tensed, too. He took a deep breath and hummed a few bars of Eine kleine Nachtmusik to calm them both. With one hand, he tilted her to the side to study the small piece of metal that would determine his fate.

The orange tag bore the number sixteen. The worst of all.

He wanted to throw her out the window, as far from him as possible, and pretend he'd never seen her. He could. The soldier didn't know what the tag meant. She'd have a few days, perhaps weeks, of precious freedom before she succumbed, and he would be safe.

"How'd a monkey get in here?" The soldier seemed charmed by the little creature. "He's a cute little guy."

"It is a female monkey." As if that mattered.

The thick bulletproof windows had a complicated latch, but the soldier would undo it for him, if he asked. He could not ask. He was a scientist first. This monkey must never be freed. Indeed, she must be contained at all costs.

Because she was infected.

She'd been infected only a few days before, but the infection ran its course quickly in primates. The danger already swam in her rich red blood. Incurable.

He remembered her now, recognized the distinctive shock of golden fur above her brows. She had been the most docile of animals, before. But she might not be docile now. He must not agitate her.

"Find a cage," he said quietly.

He stroked a finger along her warm cheek, and she followed the movement with round eyes the same shade of brown as the soldier's. Smiling, he hummed to her, while she relaxed in his arms. He drew her close to his chest and cradled her like a baby. She reached up and left an oily smudge across the right lens of his glasses.

The soldier looked blankly around the car. The doctor watched him go through the cupboards with methodical efficiency. The young man pulled out paper, pens, liquor, snacks, a towel, but nothing to contain the monkey.

If they could not imprison her, they would have to kill her. The doctor could have done it easily, but a deep wound ran along the palm of his hand where he had cut himself yesterday when slicing bread. If the monkey's blood entered his cut, he might become infected, too.

"You must kill her." He lifted the animal up toward the soldier. She weighed about five and a half kilos—he translated the metric measurement because he was in America now—twelve pounds, not much more than a human newborn.

"It's only a monkey." The soldier made no move to take the warm furry body.

"Take her," the doctor ordered.

The monkey's eyes widened as if she knew what he intended. Lightning fast, she sank her teeth into the doctor's thumb. Her sharp canines grated against his phalange bone, and his grip weakened. She squirmed free of his wounded hand and landed on the floor on all fours like a cat.

Holding his bloody hand, the doctor stumbled back against the wall of the car. He cursed. Pain throbbed through his thumb, but that was not the worst of it.

A harsh screech rose from her throat. His blood dripped from her bared fangs and fell onto the floor. She trembled and swiveled her head from side to side as if she saw enemies everywhere. She probably did.

While the soldier gaped at the angry creature, gun lax in his hands, she leaped onto his knee and climbed him like a tree, little hands and feet gripping the folds of his uniform. When she reached the top of his head, she leaned down to sink her teeth into his ear before leaping off his head and grasping a light fixture hanging from the ceiling of the car.

Nimble and quick, she swung along the wire toward the back door. The soldier's bullets stitched a neat line behind her, never quite catching up. Bullets ricocheted around the car, and both men dove to the floor.

When they stood, the monkey had disappeared.

The soldier cupped the bite on his ear, and Dr. Berger gripped his bleeding thumb.

"We may be infected," Dr. Berger said. "We must follow protocols."

The train engineer's surprised face stared at them through the thick glass window separating the engine from their car. The engineer was protected from them, and from the monkey. He lifted a black object with a curly cord. His radio. Good. He would explain what had happened, and proper protocols would be in place when they arrived. The danger would be contained.

Dr. Berger nodded his approval, and the man turned around again.

The doctor lifted the heavy top off a cut glass decanter that stood next to the compact steel sink, and the harsh smell of gin billowed out. That would do. He sloshed gin over his thumb. The alcohol burned like acid in his open wound, but it was not to be helped. It ran down the drain, colored pink with his blood. He tore a strip from the bottom of his white lab coat and used it to fashion a crude bandage for his thumb. Then he cleaned and dressed the soldier's wound, slow and fumbling because of his bandaged hand.

The monkey stayed hidden, and neither of them attempted to find her.

The soldier put down his gun and poured them each a glass of gin. He pointed to the bottle of vermouth, and Dr. Berger shook his head. The soldier didn't bother with any, either. Some things called for liquor straight up.

The gin burned a warm trail down his throat. His aching thumb would heal, and the chances of cross-species infection were minor. It was a mere inconvenience, but they would both have to be quarantined for a few weeks to make certain. Fortunate, indeed, that he had brought his notes. Perhaps the time in isolation would let him truly concentrate. At least there he would be spared the drudgery of meetings. He drained his glass, and the soldier filled it again.

The train jerked to a stop. Dr. Berger peered into the gloom. The row of orange light bulbs hanging from the ceiling cast faint light on ten armed soldiers standing in formation around the car—four on each side and two behind. These soldiers looked like the soldier inside the car, except that their Thompson submachine guns were raised and pointed at the train.

With his hands raised above his head and a meek expression plastered on to his face, Dr. Berger stood. He knew how to surrender. He walked toward the back door, to open it and explain to them they had nothing to fear from him or from the soldier.

"Don't open the door, sir," barked one of the outside soldiers.

Dr. Berger stood still and called through the door. "It is not airborne. You could only be infected by transfer of blood. There is no danger."

The soldier kept his weapon up.

Clanking at the front of the car told the doctor that a worker was unhooking the engine, but he could not see him. Half the lights were burnt out. Postwar rationing.

He'd have to wait until an intelligent man arrived to whom he could explain the situation properly. In the meantime, he sat and drank more gin while a new engine pushed their car down the tracks from behind after the old engine had left. There would be time to explain when they reached their destination.

He hoped.

A spike of paranoia rose in his brain, but he quashed it. He posed no threat to these men, and they posed no threat to him. They were no Nazis. Human life mattered to them.

The engine pushed his blue railroad car into a dead-end tunnel, then pulled away.

Darkness cloaked the car at the back and on both sides. He stared at the mouth of the tunnel. Soon they would send a doctor to whom he could explain the risks, and they would be released into quarantine.

Lit from behind by the lights strung from the ceiling, the silhouette of a tall man moved in front of the men with guns. The tall man carried a triangular blade and a bucket. A smaller man carrying the same curious items walked behind him. Were they setting up to disinfect the car with chemicals from their buckets? That was unnecessary, and they must know it. They wore blue overalls like workmen, not white lab coats, so they must be here to perform a different task.

Dr. Berger pressed his face against the cold bulletproof glass to watch.

The first man fumbled with rectangular objects on the ground, covering them with something from the bucket and slapping them with his blade. He'd already completed one row before the doctor realized what they were.

Bricks.

The two men were walling them in.

The gin burned through his system in an instant. Blind panic replaced it.

He yanked open the train door and jumped onto the tracks. Dank underground air hit him like a wall. The soldiers standing outside the shed raised their guns to point at him.

The bricklayers gave him frightened looks and increased their pace.

"There is no risk," the doctor said. "None. You are all safe."

He took another step toward the soldiers, tripping on a train tie.

"Don't move, sir," said a voice behind him.

He faced the soldier he had been drinking with a moment before. The man stood on the steps of the train, gun leveled at the doctor's chest. Blood had seeped through the makeshift bandage on his ear, but his dark eyes were determined.

"We are ordered to stay here. We must stay," the foolish soldier said.

"Those are bricks." The doctor pointed a white-clad arm at them. Already there was a second row. "They wall us in here now."

The soldier stared at the bricklayers as if he had never seen one. Perhaps he hadn't. He was young.

"We will follow orders," he said.

The men worked quickly and methodically—laying in a brick, covering it with mortar, and adding another next to it. If he ever built another house, he would want to hire them. He pulled himself together—his mind could not be allowed to wander, not now.

"We will die in here," the doctor said. "Together with that damned monkey."

The soldier lowered his weapon a few degrees.

That was enough. Dr. Berger walked toward the light.

"These are not the correct protocols," he called. There was no scientific reason to brick him in here. His heart sank. There might be political ones.

"Don't take another step, sir." This time, the soldier who spoke was on the other side of the bricks. His weapon aimed straight at the doctor's chest. The doctor did not doubt that the man would shoot him.

Already, the wall was up to his knees.

"I am an important man," the doctor said. "I come on the orders of your president. In his very own car. Do you not see his seal?"

The soldiers didn't seem to care about the seal. Dr. Berger waited precious seconds while more bricks were fitted into place. They did not understand him. They would not. They were burying him and his research. Something had gone wrong, and it had nothing to do with the errant monkey. Someone wanted him out of the way. His research was unpopular in certain circles. His enemies were burying it—and him along with it.

He spoke to the soldier he had just tended. "Give me your weapon."

The man looked between the German doctor and his American compatriots beyond the wall. His loyalty was clear. "No, sir."

"Do you want to die in here?" The bricks had reached waist height and climbed higher.

"If those are my orders." The young man looked shaken but resolute. There was no time to win him over.

Dr. Berger would not die in the darkness here. He must find out who had put him here. He must escape. He sprinted toward the growing wall, keeping low.

The soldier outside opened fire.

A bullet ripped into the doctor's shoulder near his neck. Another tore a bolt of fiery pain through his leg. He fell heavily to the hard ties. Steel track struck his temple. Warm blood ran down one cheek. Full darkness blinked in his head, but he fought it.

He must keep his wits about him.

His broken eyeglasses fell to the ground as he crabbed toward the entrance, using his good arm and leg. The smell of his own blood filled his nostrils like water filled those of a drowning man. He gagged on it, spit onto the wooden ties, and crawled forward.

They could not kill him. He was an important man. A doctor.

As a doctor, he must stop the bleeding in his neck, must assess the damage to his leg. But he was an animal first, and if he did not reach the ever-narrowing crack of light, his wounds would not matter.

Another row of bricks was added. Already, he would have to stand to climb through it. If Petey were here, he could have flown to freedom. The thought of his small yellow body flashing through the room and out into the light cheered him. Petey flying free.

Weakening with each motion, he dragged himself one body length, then another, until he reached the base of the newly built wall. The odor of wet cement overpowered the smell of blood. It reminded him of the summer he built his house, after he was appointed head of his research lab at the beginning of the war, when everything had seemed possible.

He grunted in pain as he hauled himself upright. His good leg took his weight, and his fingers found holds in the wet cement slopped between the bricks.

Then the light vanished.

The last brick was in place.

September 8, present day
Former Naval hospital
Guantanamo Bay, Cuba

Dr. Dubois jerked his head up at the crash of breaking glass. The windowless room held two battered steel desks, his and Dr. Johansson's, both occupied; old wooden cabinets full of beakers and flasks; a stainless steel table with a microscope and other equipment; and an incinerator in the corner to dispose of medical waste. In his immaculate lab, glass did not randomly break. Nothing was amiss here.

A distant scream, swiftly cut short, told him that the trouble was nearby.

Had a test subject escaped? He'd locked them in carefully after their last mission, when they were still tired and docile. Most of them were sick, practically dead on their feet. None of them could have gotten out.

Another crash, closer now. Something, or someone, was heading straight toward this room, and fast.

Dr. Johansson drew in a sharp breath and pushed thick glasses up on her freckled nose, magnified eyes rounded with fear. One hand touched the bright pink locket she always wore, a gift from one of her young daughters.

Dr. Dubois examined the room again, as if another appraisal might yield better results. It didn't. The only exit was through the door, and it led to a long corridor lined with more windowless rooms. All those doors were locked and those inside would not help him.

Based on the sound, the test subject had already reached the middle of the corridor. He and Dr. Johansson couldn't get past him. They were trapped in the lab.

He glanced at the thick steel door to the room. It had a stout lock, but it would not help them because the door only locked from the outside.

"Hide," he barked.

They both leaped to their feet and searched for a secure hiding place. If he emptied one of the medical-supply cabinets, he might be able to cram himself inside, but the test subject would notice medical supplies all over the floor. The creaky wooden file cabinet? It wouldn't offer more than a second of cover. Under the desk? Likewise.

He picked up a scalpel. The subjects were younger and stronger than he, with advanced combat training, but that might make them overconfident enough that he could get in a quick slash to an artery.

Dr. Johansson crossed to the massive incinerator recently procured to dispose of medical waste when this cell had been repurposed into a laboratory. It was the only place in the room large enough to fit a body. Her gaze met his, her unspoken question clear. She was a young military doctor with twin daughters in preschool and a brilliant research career ahead of her—she had much to live for. Dr. Dubois was years older than she, and his children were grown; they didn't need him like hers did, but he was a far more valuable researcher than she. He recognized opportunities that others missed. Scientifically, he was a greater loss.

Taking advantage of his hesitation, she swung inside the incinerator. He reached in and grabbed her long hair. She braced herself against the sides with her arms and legs. A handful of blond hair came loose in his hand.

He reached for the scalpel in his pocket to slash at her arms, but stopped when a thud against the outside wall warned him that young Private Henderson had fallen. He was the last guard in the corridor. The subject was nearly in the room. No time remained to fight with Dr. Johansson.

Dr. Dubois ran for the door and stood next to the door's hinges, gripping the scalpel. When the door opened, it would conceal him. If the test subject ran far enough into the room, or got distracted, the doctor might be able to slip out into the corridor and run. Not much of a plan, but he could think of nothing else. Maybe this test subject wasn't one of the brighter ones.

The steel door slammed open and crashed to a stop less than an eighth of an inch from his sweaty nose. He held his breath.

"I've come for you," said a hoarse voice.

Dr. Dubois recognized it at once—Subject 523. Not good. Subject 523 was intelligent, with formidable strength and training.

Quick footsteps crossed the lab, stopped by the computers, and resumed. A crash from the corner told him Subject 523 was breaking open an old wooden filing cabinet. He seemed to know what he wanted.

No decompensation yet, still high functioning in spite of exhaustion and illness. Dr. Dubois stopped himself from continuing the diagnosis. Not the time for that, either.

He peered around the edge of the door. Across the room, Subject 523 faced away from him. His dark hair was neatly cut, his uniform clean and pressed. From this angle, as he reached inside the broken file cabinet, he looked like a courier picking up a routine file.

He was anything but.

Subject 523 pulled an old manila folder from a wrecked drawer. The yellowed documents within were highly classified. They'd been kept hidden for decades, and for good reason. The doctor wasn't about to fight him for them.

Subject 523 stuffed the folder inside his desert camouflage jacket and half-turned toward the door. Dr. Dubois ducked below the wire glass window, straining his ears for the sound of Subject 523 moving toward him.

Silence.

He needed to distract the man for only a second, long enough to get into the corridor so he could make a break for the exit to the outside. A smooth rectangular object in his pocket had all the answers. Quickly, he lifted it out. His cell phone.

He called the only person who could help him right now. Her phone chirped.

From the incinerator.

Subject 523's footsteps hurried to the sound. Dr. Dubois slid out from behind the door and made for the corridor.

Dr. Johansson's shrieks sounded behind him.

He stumbled over the soft hand of Private Henderson in midcorridor. The young soldier lay flat on his back on the polished concrete floor. A red slash ran across his throat, a wound so deep the knife must have gouged his spine.

His head rested at an impossible angle in a pool of blood, and his sightless eyes stared at fluorescent lights embedded in the ceiling. The meaty smell of a butcher's shop hung in the air. Five minutes later and the private would have been on his lunch break.

Dr. Dubois ran past the corpse and two more blood-soaked bodies sprawled on the hard floor, throats slit. Blood had splashed against the brown doors on either side of the corridor. Those doors led to secured rooms full of other test subjects. He would find no safety there.

Men pounded against the steel doors, hurling profanities at him.

A crash from behind him. Subject 523 was close.

His foot slipped in a pool of blood, and he fell against a door. The man inside smashed his fist into the thick glass inches from Dr. Dubois's head. The glass held. He pushed himself off and ran, expecting to feel Subject 523's blade against his throat at any moment.

He burst out the exit door and into the humid Cuban afternoon, glad of the sunshine on his face and even gladder for the armed soldiers running toward him.

The door slammed back against the side of the building as Subject 523 cleared the corridor behind him. Two options: He'd leave Dr. Dubois alone, or take his revenge before the soldiers could stop him. The doctor redoubled his pace.

His right leg gave, and he collapsed onto the stinking tropical dirt. With a cry, he rolled over onto his back. Red spread across his thigh. He'd been shot. Subject 523 had shot him. The bastard.

Dr. Dubois looked back toward his building. The freed man sprinted into the jungle, his own safety clearly more important than his need for vengeance against the doctor, at least for the moment.

Hot pain shot up the doctor's leg. His heart raced and skipped in his chest. Was he having a heart attack, too? He was a middle-aged man who hadn't taken care of himself the way he should. He should have spent more time in the gym as Dr. Johansson always nagged him to—his mind sheered away from her final moments in the incinerator.

Armed soldiers surrounded him, shadows falling across his face.

"Orders, sir?" asked a burly sergeant whom he didn't recognize.

"Follow," he wheezed. He pointed in the direction Subject 523 had taken into the trees. "Don't let him leave the island."

"Yes, sir." The soldier saluted and pivoted to direct his men.

One man dropped to his knees next to the doctor and dropped a first aid kit onto the ground. A medic who barely looked old enough to be out of high school. "Are you OK, sir?"

"No," the doctor yelled. "I'm shot. Shot in the leg."

"I see that, sir." The young man's voice was infuriatingly calm. His hands fussed with a hypodermic syringe.

"Hurry, God damn it!"

"Yes, sir," he said.

The doctor barely felt the needle, but he felt the drug enter his system. The pain gave way to warmth, to a feeling of well-being. He couldn't give in to it. They had to catch Subject 523.

But he was too smart to be caught. If he didn't come back for revenge, Subject 523 would be off the island in hours. He had the training to evade capture, and he'd figure out a way to steal a boat or a plane or God knew what else. He was a skilled man, still.

Dr. Dubois must control this situation—starting with dealing with the rest of the 500 series, then hiring a man to find and sacrifice Subject 523. As bad as things were now, they would soon get much worse.

Subject 523 was infected.

And the file in his shirt would lead him to the most-populous city in the United States—New York.