In May of 1925, Edith Brennan stood at the upstairs window of number 47 Cranbrook Road and watched a cart horse die in the street. The animal had been pulling a coal wagon when its front legs buckled on the cobblestones. The coalman, a red-faced man named Mr. Griggs who had been making this delivery since before the war, stood over the horse with his cap in his hands while a small crowd gathered. Edith could hear the animal's breathing from her window — a wet, labored sound that seemed too large for the narrow street. A policeman arrived. Someone fetched a pistol. Edith turned away before the shot. She was twenty-eight years old, and she had lived on Cranbrook Road for six years, and she had never seen a horse shot before, though she would remember the sound of its breathing for the rest of her life.

In May of 1975, Sarah Kemp stood at the upstairs window of number 47 Cranbrook Road and watched a Ford Cortina backfire in the street. The car was a 1972 model, beige with a rusted wheel arch, and the backfire made a sound like a door slamming in an empty room. The driver, a young man with shoulder-length hair and a denim jacket, got out and kicked the rear tire and swore. Sarah was twenty-six years old, and she had never been to Cranbrook Road before that morning, and she was looking for something she could not name. She had taken the train from Cambridge that morning, a British Rail diesel that arrived at Liverpool Street at ten-fifteen, and she had walked from the station with a street map and a photograph of a woman she had never met.

In June of 1925, Edith joined the textile workers' union. The mill where she worked — Carstairs & Son, Cotton Spinners and Weavers, established 1873 — occupied a brick building on Whitechapel Road that had been modernized in 1910 with electric looms that ran sixteen hours a day. Edith worked the day shift, six in the morning until two in the afternoon, operating a spinning frame that filled the air with cotton dust so fine it settled on her skin like a second layer of flesh. The union organizer was a woman named Florence Dawlish, who had lost two fingers to a carding machine in 1919 and had been organizing ever since. Florence wore men's trousers and smoked Woodbines and spoke in a voice roughened by years of shouting over machinery. She told Edith that the Carstairs pay scale was sixpence below the district standard and that the ventilation system violated the Factory Act of 1901. Edith had never thought about ventilation systems. She had thought about paying the rent on number 47, which was twelve shillings a week, and about the price of bread, which had gone up again, and about whether David Cohen would ever look at her the way she looked at him.

In June of 1975, Sarah found the diary. She had been staying at a bed-and-breakfast on Mile End Road — four pounds fifty a night, shared bathroom, a landlady who served tea at seven and toast that was always slightly burnt — and she had spent three days walking Cranbrook Road from end to end, taking photographs with her Pentax Spotmatic, interviewing residents who could remember the interwar years. The diary was in a trunk in the attic of number 47, which was now occupied by a Pakistani family named Haq who had come to London in 1968. Mrs. Haq showed Sarah to the attic apologetically — "We never go up there, terribly dusty, I'm afraid" — and there, under a stack of yellowed newspapers from 1953, was a tin box with a rusted clasp. Inside the box was the diary. The cover was brown leather, cracked at the spine. The handwriting was small and precise, in faded black ink. The first entry was dated January 4, 1925. The last entry was dated June 19, 1926. Sarah sat on the attic floor, surrounded by dust motes floating in the light from a single dormer window, and began to read.

In July of 1925, David Cohen asked Edith to walk with him along the Regent's Canal. It was a Sunday, the one day the mill was closed, and Edith wore her best dress — a calf-length floral print she had bought at Petticoat Lane market for four shillings — and David wore a brown suit that was slightly too large for him, a hand-me-down from his older brother. David was twenty-nine, a tailor's apprentice on Commercial Road, the son of a Polish Jew who had come to London in 1895 and set up a shop on Wentworth Street. He had kind eyes and a slight stammer that got worse when he was nervous. They walked along the canal towpath past barges carrying coal and timber, past children fishing with string and bent pins, past a man playing a concertina on the steps of a lock-keeper's cottage. David told Edith about his father, who had walked from Warsaw to Hamburg in 1894 with nothing but a sewing kit and a letter of introduction from a rabbi who had since died. He told her about the tailoring trade, about the difference between English wool and Italian wool, about the way a properly cut jacket should hang from the shoulders. Edith listened and thought about the cotton dust in her lungs and the way David's hands moved when he talked — small, precise gestures, the hands of a man who worked with needles and thread. When they reached the lock at Old Ford, David stopped walking and turned to face her, and the stammer got very bad, and he asked her to marry him. Edith said yes before he finished the question.

In July of 1975, Sarah found the photograph. It was tucked between the pages of the diary, a small print on heavy paper, slightly curled at the edges. The photograph showed a man and a woman standing on the steps of a synagogue on a street Sarah did not recognize. The man wore a black suit and a bowler hat. The woman wore a white dress and a veil. They were young — younger than Sarah was now — and they were looking at each other, not at the camera, and their faces held an expression that Sarah recognized from her own reflection on certain mornings, an expression that meant I am standing at the beginning of something I do not fully understand. On the back of the photograph, in the same small precise handwriting: Edith and David, 28 September 1925, Great Garden Street Synagogue. Sarah turned the photograph over and over in her hands. She had known about David Cohen in the abstract — her mother had mentioned him once or twice, an old man who died before Sarah was born, a grandfather she had never met — but the photograph made him real in a way that unsettled her. The photograph made him a person who had stood on a street in 1925 and looked at a woman the way Sarah had once looked at a boy on a train platform, a boy whose name she could no longer remember but whose face had lingered for months.

In December of 1925, the ventilation system at Carstairs & Son failed. It was a cold month, the coldest December since records began, and the boiler that powered the ventilation fans had frozen and cracked during a night when the temperature dropped to nine degrees Fahrenheit. The mill owner, a man named Harold Carstairs who had inherited the business from his father and who lived in a house in Hampstead with nine bedrooms, declined to repair the boiler. The repair would cost forty pounds. Instead, he instructed the workers to open the windows. Edith worked her spinning frame in a room where the temperature was thirty degrees and the cotton dust was so thick she could not see the far wall. She wrote about it in her diary: The dust is like fog, she wrote. The dust is like something alive. Florence Dawlish called a meeting in the basement of the Methodist church on Mile End Road, and sixty-seven workers attended, and they voted to strike. The strike lasted eleven days. On the twelfth day, Harold Carstairs agreed to repair the boiler. He also agreed to raise wages by three pence per hour. Edith came home to number 47 Cranbrook Road with frostbite on two fingers of her left hand and the knowledge that she had been part of something. David kissed the frostbitten fingers and held them against his chest and said, "You are the bravest person I have ever known." The fingers healed, mostly. For the rest of her life, they would ache in cold weather.

In December of 1975, Sarah stood in the basement of a Methodist church on Mile End Road and tried to feel her grandmother's presence. The church was still there, though the congregation had dwindled to thirty-seven members and the roof leaked and the organ had not been played in two years because no one could afford to repair the bellows. The caretaker, an elderly man named Mr. Wetherby who had been with the church since 1938, showed Sarah the basement and told her about the strike of 1925. "Your grandmother was here," he said. "I wasn't, of course. I was a boy in Manchester. But I heard the stories. They said she was the one who convinced them to hold out. The owner offered a penny raise on the third day and most of them were ready to take it. Your grandmother said no. She said the ventilation was the main thing. She said they couldn't go back until the ventilation was fixed." Sarah listened and tried to reconcile this woman — this organizer, this strategist, this person who had faced down a mill owner in 1925 — with the other woman she was discovering in the diary: the wife who cooked Friday night dinners, the mother who mended clothes by candlelight, the neighbor who brought soup to the sick. Both women were her grandmother. Both women were true. She could not hold them both in her mind at the same time.

In March of 1926, the General Strike loomed. The miners had been locked out. The Trades Union Congress was preparing to call a general walkout. Edith and David sat at their kitchen table on Cranbrook Road and discussed whether David should join. David was not a union man — the tailoring trade was fragmented, small shops, no collective bargaining — but he believed in the cause. Edith believed in the cause too, but she was three months pregnant, though she had not yet told David. She would tell him in April, after the strike began, in a note she left on the kitchen table before she went to walk a picket line at Carstairs & Son. The note said: There is something I should have told you. I am sorry. I am going to the mill. I will come home. I promise.

In March of 1976, Sarah read her grandmother's last diary entry. It was dated June 19, 1926. The final entry was short, four sentences, written in a hand that was shakier than the rest of the diary: The baby is coming. David has gone to fetch Mrs. Morgan from number 23. The light this morning is very beautiful. I am not afraid. Sarah closed the diary and sat in the attic of number 47 Cranbrook Road and wept. She wept for her grandmother, who had given birth to a daughter named Catherine on June 20, 1926, and had died of postpartum hemorrhage on June 22, 1926, three days before her twenty-ninth birthday. She wept for her mother, who had been raised by David Cohen and who had never spoken about her own mother except to say, once, when Sarah was twelve and had asked about the grandmother she never met, "She was very brave. She was braver than I could ever be." And she wept for herself, for the woman she was becoming, for the question she had come to Cranbrook Road to answer: whether the choices you make in one moment can illuminate or burn the lives of people who come after, whether the light you create for your own time reaches forward or backward or not at all.

She had come to Cranbrook Road because she was at a decision point in her own life. She had finished her sociology degree at Cambridge. She had been offered a research position at the University of Essex and a teaching position at a comprehensive school in Hackney and a third possibility she had not told anyone about — a man named Richard who had asked her to move to Australia with him. The research position was prestigious. The teaching position was meaningful. Richard was kind and handsome and almost certainly a mistake. She had come to Cranbrook Road hoping to find something — a sign, a lesson, a pattern — that would tell her which choice was right. What she found instead was a woman who had made choices of her own fifty years earlier, choices that had been right in 1925 and that had echoed forward in ways Edith could never have predicted. The strike had fixed the ventilation system. The raise had helped pay for the baby's crib. And Edith had died anyway, of a thing no choice could have prevented, leaving behind a husband who would never remarry and a daughter who would grow up motherless and a granddaughter who was now sitting in an attic in 1976 trying to understand how a life could be both a triumph and a tragedy, both light and burning, both something that illuminated the world and something that was consumed by it.

That evening, Sarah walked the length of Cranbrook Road from end to end. The street was quiet under the June sky, the same sky her grandmother had looked at from a different window, a different body, a different life. The houses were the same houses, the brick was the same brick, the cobblestones under the asphalt were the same cobblestones that had borne the weight of a dying cart horse in 1925. Sarah stood in front of number 47 and looked up at the upstairs window. She imagined her grandmother standing there, a young woman in a floral dress, watching a horse die in the street and not knowing that in fourteen months she would be dead herself. She imagined her grandmother looking out at a world she was trying to make better in ways that were both large and small, organizing strikes and bringing soup, facing down mill owners and mending clothes by candlelight. She imagined the light that passed through that window in 1925 — the same light that was passing through it now, the same photons from the same sun traveling the same distance at the same speed — and she understood, in a way she could not have articulated, that the light was the same but the frequency had shifted. All the colors had shifted toward red. Everything her grandmother had built — the union, the marriage, the child, the hope — was still there, was still present, was still traveling outward at the speed of light, but it looked different from where Sarah stood. It looked like something you could not touch but could still feel. It looked like a photograph of two people looking at each other on the steps of a synagogue in 1925. It looked like a diary entry written in a shaky hand on the last day of a life. It looked like a woman standing at a window in 1976, looking at a street that was both the same and completely different, knowing that she was standing in the light of a star that had already died.