On the morning Augustus Hartwell first felt the crack forming inside him, the elevated railway on Sixth Avenue screamed past his office window and the steam rose white against a November sky the color of old pewter. It was 1883. He was fifty-one years old, and he had not slept more than three hours a night for eleven months.

The office occupied the entire top floor of the Hartwell Building on Broadway, a twelve-story monument to structural steel that he had financed with bonds sold to men who would later lose their savings when those same bonds proved to be secured against rail lines that existed only on paper. The irony had not been lost on him then. It was not lost on him now. Nothing was ever lost on Augustus Hartwell; that was precisely the problem.

His secretary, a pale young man named Whitmore who wore celluloid collars and smelled faintly of camphor, placed the morning correspondence on the corner of the mahogany desk. Augustus did not look up. He was staring at the steam-driven elevator indicator on the wall, watching the brass arrow tick from floor to floor, and he was thinking about the temperature at which iron changes its crystalline structure.

One thousand three hundred and forty degrees Fahrenheit. At that temperature, the body-centered cubic lattice of ferrite transforms into the face-centered cubic structure of austenite. The iron does not bend. It does not gradually soften. It becomes something else entirely, in an instant, at a precise thermodynamic threshold.

He had read this in a metallurgical journal the previous evening, sitting alone in his Fifth Avenue brownstone while his wife attended a charity tableau at the Academy of Music. He had read it three times. Then he had poured himself four fingers of Kentucky bourbon and stood at the window watching the gas lamps flicker along the avenue, and he had thought: I understand this. I understand this completely.

The pressure had been building for years. It had begun, perhaps, in 1877, when the great railroad strike had swept across the country and his own rail lines had been blocked by mobs of workers in Pittsburgh, men whose wages he had cut three times in two years. He had telegraphed the governor of Pennsylvania from this very office, standing at this very window, and he had dictated a message that contained the phrase "give them a rifle diet for a few days and see how they like that kind of bread." The message had been leaked to the newspapers. Twenty-six strikers had been shot dead by state militia the following week.

Augustus had felt nothing at the time. He had felt nothing because he had trained himself to feel nothing. The training had begun in 1863, when he was thirty-one and serving as a quartermaster contractor for the Union Army, supplying boots that disintegrated in mud and blankets that had been rejected by the Army of the Potomac as unfit for horses. He had learned then that conscience was a luxury that men who intended to build empires could not afford. He had walled it off, brick by brick, in a corner of his mind that he never visited.

But the bricks do not hold forever. They do not hold because the conscience is not a structure one builds; it is a gas that fills whatever container you place it in, and under sufficient pressure, it will find the cracks.

The cracks had begun appearing in 1881.

That was the year his youngest daughter, Eleanor, had contracted scarlet fever. She was seven years old, with hair the color of winter wheat and a habit of pressing her small hand against his cheek when he returned from the office. The fever had taken her in four days. Augustus had stood at her bedside in the brownstone on Fifth Avenue, watching the doctors bleed her with leeches according to the best medical practice of the day, and he had felt something shift in the walled-off corner of his mind. Not a collapse. Just a shift. A hairline fracture.

His wife, Margaret, had retreated into laudanum and séances. She spent her evenings now in the parlor with a medium named Madame Rostova, a Hungarian woman who claimed to channel the spirits of the dead through a speaking trumpet. Augustus could hear the muffled drone of the trumpet through the floorboards when he sat alone in his study, and sometimes he thought he heard Eleanor's voice in the hollow brass echo, and he would pour himself another bourbon and stare at the metallurgical journals until the words blurred.

The second crack had come in 1882, when the Bessemer converter at his Pittsburgh plant had exploded during the night shift. Seventeen men had been engulfed in molten steel. Their bodies had never been recovered; they had become part of the alloy, their calcium and phosphorus absorbed into the iron lattice, their carbon contributing to the precise percentage that made Hartwell Steel the strongest rail stock in the eastern United States.

Augustus had attended the memorial service. He had stood in the rain at the edge of the mass grave and watched the widows weep, and he had felt something crack deeper inside him, something that ran through the brick wall like a fault line through bedrock. But he had not broken. The wall had held. He had returned to New York on the overnight train and the next morning he had negotiated the acquisition of the Allegheny Valley Railroad at forty cents on the dollar, and the men who had owned that railroad had wept too, but Augustus had not seen them weep because he had sent Whitmore to close the transaction.

The third crack, the deep one, the one that ran all the way to the foundation, had come in September of 1883, just two months before this November morning. It had come at Delmonico's.

He had been dining with a consortium of Tammany Hall ward bosses, men who wore diamonds in their cravats and spoke of the city as if it were a carcass to be carved. The conversation had turned to the new tenement housing bill, which Augustus opposed because it would require him to install gas lighting in the stairwells of the forty-seven buildings he owned on the Lower East Side. The cost, he had calculated, would reduce his quarterly dividend by one and three-eighths percent.

A young alderman named O'Malley, drunk on claret and ambition, had leaned across the table and said: "Mr. Hartwell, I understand your position, but surely you cannot expect families to live in darkness. There are children in those buildings."

And Augustus had opened his mouth to reply with the answer he had given a hundred times before — that poverty was a moral failing, that charity encouraged indolence, that the market corrected all inequities in time — but the words had not come. Instead, he had seen, with a clarity that felt like being struck by lightning, the face of a child he had never met. A girl, perhaps seven years old, with hair the color of nothing in particular, climbing a dark stairwell with a candle in her hand. He had seen her stumble. He had seen the candle fall. He had seen the flames catch the hem of her dress.

He had excused himself from the table and walked out onto Fifth Avenue. The autumn air had been crisp with the smell of horse manure and roasting chestnuts. He had stood on the sidewalk and pressed his hand against his chest, and he had felt something moving inside him, something that had been walled away for twenty years, pressing against the bricks with a force that terrified him.

He had not gone back into Delmonico's. He had walked home through the gaslit streets, past the brownstones with their drawn curtains and their warm yellow windows, and he had felt the thing inside him pacing like a caged animal.

And now it was November. The elevated railway screamed past his window. Whitmore hovered at the edge of his desk with the morning correspondence. And Augustus Hartwell was thinking about the austenitic transformation point.

"Sir," Whitmore said, "there is a delegation here to see you. From the Tenement Reform Committee. They have been waiting since eight o'clock."

Augustus turned from the window. His face, which the newspapers had described as "granitic" and "impassive" and "the mask of a man who has forgotten how to weep," was pale and tight. His eyes, which had watched twenty-six men die in Pittsburgh without blinking, were red-rimmed and raw.

"Send them away," he said.

"Sir, they have come from Albany. They have letters from the governor."

"I do not care if they have letters from the Almighty. Send them away."

Whitmore hesitated. In eleven years of service, he had never heard Augustus Hartwell raise his voice. The industrialist's power had always been in his stillness, his immovability, his ability to wait out any opponent with the patience of a glacier.

But the glacier was melting. Whitmore could see it. He could see the cracks spreading across the granite face, could hear the tremor in the voice that had once dictated the terms of surrender to half the railroads in the Midwest.

"Sir," Whitmore said carefully, "perhaps you should rest. You have not been yourself these past weeks."

Augustus laughed. It was not a pleasant sound. It was the sound of something breaking.

"Myself," he said. "Which self would that be, Whitmore? The one who built this building on the bones of seventeen men in Pittsburgh? The one who let his daughter die while he negotiated a freight contract in Chicago? The one who sits in this office and signs papers that determine whether children in the Bowery will have light in their stairwells?"

Whitmore said nothing. There was nothing to say.

Augustus walked to the window and looked down at Broadway. The street below was a river of black carriages and dark-coated men, of newsboys shouting headlines and women in bustled skirts picking their way across the cobblestones. The city that he had helped to build. The city that had made him one of the twelve richest men in America.

"I have been two men," Augustus said quietly. "For twenty years, I have been two men. One who builds. One who destroys. One who signs papers. One who sees the faces at night." He turned from the window. His eyes were wet. "Do you know what happens to iron at thirteen hundred and forty degrees, Whitmore?"

"No, sir."

"It changes. Not gradually. Not slowly. At a single point, a single degree, it becomes something else. The crystalline structure rearranges itself. What was one thing becomes another, in an instant, and it can never go back."

He walked to his desk and opened the top drawer. Inside, amid the contracts and the correspondence and the stock certificates, was a revolver. A Colt Single Action Army, nickel-plated, with ivory grips. He had purchased it in 1863, when he had first begun to fear that the men whose fortunes he had destroyed might come looking for him.

"Sir," Whitmore said, his voice rising, "sir, please —"

But Augustus Hartwell did not raise the revolver to his head. He raised it toward the door of his office, toward the mahogany panels behind which the delegation from Albany was waiting, toward the city and the century and the civilization that had demanded of him that he become two men.

"Send them in," he said.

"Sir?"

"Send them in, Whitmore. All of them. The committee. The aldermen. The newspaper reporters. Anyone who wishes to know what Augustus Hartwell thinks about the tenement housing bill."

Whitmore backed toward the door, his face as pale as his celluloid collar. He had seen his employer in many moods — cold, calculating, implacable, occasionally wry. He had never seen him like this. The industrialist's face was no longer granite. It was molten.

"Sir, the revolver —"

"Is not for them," Augustus said. "It is for the other man. The one who has been living in this body for twenty years. The one who signed the papers and cut the wages and watched the children die. I am going to kill him, Whitmore. Right here. Right now. In front of witnesses."

He placed the revolver on the desk and sat down in his chair. His hands were trembling, but his voice was steady. The cracking had stopped. Something had given way. The crystalline structure had rearranged itself.

"I will sign whatever they put in front of me," he said. "I will fund the installation of gas lighting in every tenement I own. I will testify before Congress about the railroad bonds. I will name the men at Tammany Hall who took bribes. I will tell the newspapers about the boots that disintegrated in the rain at Gettysburg. I will tell them everything."

Whitmore stood frozen in the doorway. The steam elevator indicator ticked from floor to floor. The elevated railway screamed past the window. The city hummed with the sound of seven hundred thousand souls going about their business, unaware that one of the titans who shaped their world was dissolving before their eyes.

"You will destroy yourself," Whitmore whispered.

"No," Augustus said. "I will destroy the other man. The one who should never have existed. The one I built to survive." He picked up the revolver and looked at it with something that might have been tenderness. "Thirteen hundred and forty degrees, Whitmore. That is the temperature at which iron becomes austenite. It is a phase transition. It is irreversible. The iron does not go back."

He stood up and walked to the window one last time. Below him, a newsboy was shouting the evening edition. A carriage was turning onto Fifth Avenue. A woman in a green dress was walking a small dog past the entrance to the Hartwell Building. The gas lamps were beginning to flicker on in the gathering dusk.

"Do you know what I feel?" Augustus said. "I feel light. As if I have been carrying a second man on my back for twenty years, and I have finally set him down."

He turned from the window and faced the door.

"Send them in, Whitmore. Send them all in. And then send a telegram to Margaret. Tell her to sell the brownstone. Tell her I will not be coming home tonight. Tell her the wall has fallen. Tell her that two men cannot occupy the same body anymore, and one of them has decided to die."

Whitmore opened the door. The delegates from Albany filed in, ten men in dark suits with leather portfolios and worried expressions. Behind them came a reporter from the Tribune, whom Whitmore had summoned with a gesture that he did not remember making. Behind the reporter came two aldermen and a police captain and a woman from the Ladies' Home Missionary Society who had been waiting in the corridor for three hours to petition Augustus about a school for immigrant children.

They filled the office. They saw the revolver on the desk and they stopped, their faces frozen in mid-expression, their portfolios clutched against their chests.

Augustus Hartwell looked at them. He saw, in their faces, the same fear that he had seen in the faces of his competitors, his workers, his wife, his daughter before she died. The fear of a man who holds absolute power. The fear of a man who has no conscience.

But he no longer had absolute power. He had surrendered it, at the precise temperature of transformation, and in its place he had found something that felt like peace.

"Gentlemen," he said, "and lady. I have something to tell you. It will take some time. It will not be pleasant. But when I am finished, the man who built this empire will no longer exist, and the man who remains will be someone I have not met in twenty years. I hope you will find him acceptable."

He picked up the revolver. The delegates flinched. But Augustus did not point it at them. He pointed it at the portrait on the wall behind his desk, the portrait of himself that had been painted in 1879 by a French artist whose name he could no longer remember.

He fired once. The bullet tore through the painted face and lodged in the plaster behind it. The sound was like a door slamming shut on a room that had been sealed for two decades.

"There," Augustus Hartwell said, setting the revolver down on the desk. "He is dead. Now let us begin."

And he sat down, and he began to speak, and the words that came out of him were not the words of the industrialist or the titan or the robber baron. They were the words of a fifty-one-year-old man who had once loved his daughter, who had once believed that the world could be made better, who had buried his conscience so deep that he had forgotten where to find it. They were the words of a man who had reached the temperature at which iron changes, and who had changed, and who would never go back.

Outside the window, the gas lamps blazed orange against the November dark. The elevated railway rattled north toward Harlem. The city that Augustus Hartwell had helped to build continued its relentless motion, indifferent to the transformation occurring in the top-floor office of the Hartwell Building. But somewhere on the Lower East Side, in a tenement stairwell that had never known the warmth of gaslight, a child was climbing the stairs with a candle in her hand, and she did not stumble, and the candle did not fall, and the darkness held its breath and waited for the light.