I

Eleanor Hargreave stood at the window of the third-floor flat on Hammersmith Grove on a morning in April 1925 and watched the street wake. The gas lamps were still lit, their blue flames visible even in the daylight, and the milk cart had not yet come because the milkman was a man named Thomas who was unreliable and Eleanor had noted this in a list she kept on the back of an envelope that was now beneath the sugar jar, and the list had other names on it: the butcher who overcharged on Tuesdays, the woman who lived downstairs who played the piano at eight in the evening when Eleanor needed to write, the man who sold newspapers on the corner who had a face like a closed door and never smiled, and Eleanor had written closed door face on a scrap of paper and put it in her desk drawer and forgotten it and found it again three weeks later and understood that she had named the man in the same way she had named the piano and the overcharging and the unreliable milkman, as an inconvenience in a life that was composed of inconveniences that accumulated like dust on a shelf that was never wiped.

Eleanor was twenty-eight and she wrote for the Pall Mall Gazette, a small department of the paper that was called Social Notes and was considered less serious than the political reporting and the financial correspondence and the war stories, and Eleanor did not mind because she was interested in social things and social things were the things that happened in the spaces between the big events and the big events were happening everywhere, in India where her brother had been posted as a junior administrator and in Africa where regiments were stationed and in Ireland where the men with closed door faces were gathering in rooms and talking about freedom and the word freedom appeared in Eleanor's writing so often that she had begun to wonder if freedom was a luxury that only people who had their own flat on the third floor of a building they did not own could afford to think about.

She wrote about tea parties and charity bazaars and the visiting American diplomats and the new cinema on Fulham Road that had electric lights and a floor that was not made of wood and the ladies who wore hats that were too large for their faces and the gentlemen who stood in doorways and smiled with their mouths and not with their eyes, and Eleanor wrote these things because they were required and because the editor, a man named Arthur Pendelton with a mustache that was wider than his face, said that women readers wanted to know about the social calendar and the social calendar was a calendar of visibility, of who was seen and where and with whom and in what company and in what light, and invisibility was not a topic that appeared in the social notes because invisibility was not social and social things were by definition visible and Eleanor had written a paragraph once about the women who washed the flags for the regiment and who stood in alleys behind the barracks and scrubbed white cotton in buckets of gray water and their hands were red and cracked and no one saw them and Arthur had cut the paragraph and said we do not write about laundry and Eleanor had accepted this because laundry was not news and news was what was visible and the invisible world was a world that existed but did not appear in the paper and Eleanor's job was to make things appear and she had accepted this job and the acceptance was the first thread.

II

Margaret Hargreave stood at the window of the third-floor flat on Hammersmith Grove on a morning in October 1975 and watched the street change. The gas lamps were gone, replaced by electric ones that were taller and brighter and threw a light that was not yellow but white and did not flicker and did not need to be lit by a man with a ladder and a match and a coat that smelled of gas and Margaret had never met the man with the ladder because she had moved into the flat six months earlier and the man with the ladder was part of a street that had existed before she was born and would have existed if she had not been born and his absence was as visible as his presence had been to Eleanor, who had lived in this flat fifty years earlier and whose name appeared in no record that Margaret had been able to find and whose existence was a fact that lived in a box in the attic of the house in Fulham where Margaret's mother kept things that were not useful but could not be discarded, and the box contained a bundle of letters tied with ribbon, a photograph of a woman at a window, and a sheaf of newspaper clippings that were brittle and yellowed and had the word Social Notes at the top in ink that was fading to brown.

Margaret was twenty-six and she worked at the London School of Economics as a research assistant in the sociology department, a department that was studying urban communities and the changes in British neighborhoods since the war and the disappearance of the old streets and the old shops and the old men with ladders and Margaret's job was to go to streets like Hammersmith Grove and talk to the people who lived there and ask them about their neighbors and their children and their shops and their memories and write it down in a notebook with a black cover that Margaret had bought at a shop on Charing Cross Road and the notebook filled quickly because the people on Hammersmith Grove had memories and memories were the currency of the street and the street was running out of currency and the shops were changing and the butchers were becoming Indian takeaways and the bakeries were becoming estate agents and the estate agents had windows that were too clean and signs that were too bright and men with closed door faces who did not sell anything and did not smile and did not need to because the signs did the smiling for them and the word visibility appeared in Margaret's research notes as often as it had appeared in Eleanor's newspaper, and the word was different now, not about who was seen at a tea party but about which businesses were visible to the city council and which were not and which neighborhoods received services and which did not and which people were counted in the sociology department's research and which were not counted because they worked in offices and their invisibility was a privilege and the invisibility of the women who washed the flags in alleys behind the barracks had been an invisibility of erasure and the invisibility of the men in offices was an invisibility of comfort and Margaret was trying to understand the difference and the understanding was the second thread.

III

The letter was written on April 14, 1925, and it was addressed to No address because Eleanor did not have an address to give, her flat was hers only by permission of her father who owned the building and who wrote to her every Sunday and asked when she would marry and she wrote back every Monday and said not soon and the letters were stored in a desk drawer beneath the scrap of paper that said closed door face and the letter of April 14 was a different kind of letter. It was not to her father. It was to nobody and to everybody and it was a letter that she wrote after reading a report in the Times about the conditions of female workers in the flag-making factories at Enfield, three hundred women, mostly young, mostly from the East End, working twelve-hour days for wages that were calculated by piece and the piece rate had been reduced by four pence in the previous month and the women had organized a meeting and the meeting had been broken up by police and the report was written in the language of distance and objectivity and the reporter had not spoken to any of the women and had not visited the factory and had not seen the red hands and the cracked knuckles and the gray water in the buckets and the cotton flags that were white and would be seen at parades and the women who made them would not be seen and Eleanor had written about this in the Social Notes department and the paragraph had been cut and the cutting had been done by Arthur Pendelton who had said we are a newspaper not a conscience and Eleanor had said that was a reductive framing of our institutional mission and Arthur had said that was a long way of saying you want to be a pamphlet and Eleanor had said nothing and the nothing was the space where the thread was formed.

Eleanor's letter of April 14 was seven pages long. It described the flag-makers in detail, with names and ages and addresses, information she had gathered from a contact at the Home Office who was a woman named Beatrice who worked in the statistics division and who had whispered the names to Eleanor in the reading room of the British Museum while men in jackets turned pages of encyclopedias and the sound of the turning was like the sound of rain and Eleanor had written the names in a notebook that she kept in her bag and brought home and read by lamplight and copied into the letter and the letter was not sent. It was filed in a drawer beneath the closed door face scrap and the Father letters and the envelope with the list of inconveniences and the letter sat there for fifty years while the drawer accumulated dust and the building on Hammersmith Grove accumulated tenants and the street accumulated shops and the shops accumulated and disappeared and the city accumulated and the letter did not accumulate anything except time and time is not a substance and it has no weight and it cannot be seen and it is the material of invisibility.

IV

The photograph was found in the box in the attic in Fulham on a Saturday in March 1976, six months after Margaret had moved into the flat on Hammersmith Grove and three months after she had submitted her first research report to the sociology department and the report had been well-received and the well was a word that appeared in the margin of the report in Arthur Pendelton's grandson's handwriting, the department head, a man named Richard Pendelton who had the same wide mustache and the same smile with the mouth and not with the eyes and Margaret had thought, is this a family trait or a professional requirement for men who study things they do not understand.

The photograph was of a woman at a window. The woman was young, perhaps twenty-eight, and she was wearing a dress with a high collar and long sleeves and her hair was pulled back and her expression was neither sad nor happy but was the expression of someone who was looking at something that was not the camera and the window was open and the street was visible below, a street of gas lamps and horse-drawn carts and women in long dresses and men in hats and the photograph had been taken from behind, from inside the room, and the photographer had stood at the woman's shoulder and pressed the shutter and the exposure had been long enough that the woman's face was in shadow and the street below was bright and the people on the street were visible and the woman at the window was not, and Margaret held the photograph and turned it over and there was no date and no name and on the back, in faded ink, was written Eleanor and the thread from 1925 reached across fifty years and touched Margaret's fingers and the touch was not supernatural and not magical and not anything that could be proved and the proof was that Margaret put the photograph down and walked to the window of the flat on Hammersmith Grove and looked at the street and saw the electric lamps and the bus that ran every fifteen minutes and the Indian takeaway and the estate agent with the too-clean window and the man with the closed door face who worked at the estate agent and did not smile and did not sell and Margaret understood that the woman at the window had looked at this same street and seen it from the same angle and the street was different and the street was the same and the woman below had been invisible to the camera the way the flag-makers were invisible to the reporter the way the men in offices were invisible to the sociology department the way Eleanor was invisible to her father who wrote every Sunday and asked about marriage the way Margaret was invisible to Richard Pendelton who said her report was well done and moved on to the next one and the thread was the visibility that was chosen and the invisibility that was imposed and the two were always present and the choosing was Eleanor writing a letter that was not sent and Margaret writing a report that was well-received and filed and forgotten and the filing was the same action and the forgetting was the same result and the result was the thread, a single thin line connecting a woman at a window in 1925 to a woman at a window in 1975, both looking at the same street, both invisible to the camera, both invisible to the paper, both invisible to the department, and both right in their own reference frame, Eleanor right to want to write about the red hands and Margaret right to write about the right hands, the hands that signed the checks and closed the deals and owned the buildings, and the thread was the line between them, visible only when both timelines were held in the same mind at the same time, which was a thing that could not be done, and the holding was the work and the work was invisible and the invisibility was the point and the point was the thread and the thread was on Hammersmith Grove and the street did not know it and did not need to know it and the thread did not need to be known to hold.

V

Eleanor died in 1962, at the age of seventy-one, in the flat on Hammersmith Grove that she had returned to after her father died and inherited and sold the publishing career she had abandoned in 1935 when Arthur Pendelton had retired and she had stayed on as a freelance contributor and the contributions had become fewer and the letter that had not been sent had remained in the drawer and the drawer had been closed and the flat had been kept and kept and kept and the keeping was a form of visibility, of saying I was here and the here was a flat on the third floor of a building on Hammersmith Grove and the here was a desk with a drawer and the drawer held a letter and the letter held names and the names were women who made flags that were white and seen and the women were not and Eleanor had seen them and the seeing was the thread and the thread held for fifty years after she died and then the flat was vacated and sold and renovated and the desk was discarded and the drawer was opened by men who wore boots in the house and carried furniture down the stairs and the letter was in the drawer and the letter was read by one of the men who wore boots and he was a man with a face that was not a closed door but was something softer and he read the letter and he did not know what to do with it and he put it back in the drawer and the desk was carried out and the letter was left behind and it lay on the floor of the empty flat beneath a layer of dust that was the same dust that had been on the shelf that was never wiped and the dust did not know it contained the particles of a letter and the letter did not know it contained names and the names did not know they contained women and the women did not know they contained a street and the street did not know it contained a thread and the thread did not know it connected a window in 1925 to a window in 1975 and the woman in 1925 and the woman in 1975 did not know they were the same person in different reference frames and both were right and the rightness was the thread and the thread was on Hammersmith Grove and the street continued to change and the invisibility continued and the visibility continued and the ledger was balanced in a hand that was dust and the dust was on the floor and the floor was bare and the flat was empty and the building stood and the street stood and the thread held in a language that had no words.

VI

Margaret left Hammersmith Grove in June 1976. She found a flat in Kilburn that was smaller and cheaper and closer to the LSE and she packed the box from the attic in her mother's house and brought it to Kilburn and placed the box on a shelf in the kitchen and the photograph of Eleanor at the window was on top and Margaret looked at it every morning while she drank tea from a cup that was chipped at the rim and the chip was visible and the visibility was small and the small things were accumulating in Margaret's life like the inconveniences had accumulated in Eleanor's, the chipped cup and the cheap rent and the small flat and the research that was well-received and filed and forgotten and the report about the estate agents and the Indian takeaways and the men with faces that were not closed doors but were something softer and softer than closed was the direction the street was moving and the movement was progress and progress was visible and the people who made progress were visible and the people who made the flags were still visible only to the people who chose to see them and the choosing was the thread and the thread held and Margaret sat at her desk in Kilburn and wrote her next report and the report was about visibility and invisibility in urban communities and the report was well-received and the well was in the margin and the margin was invisible and the invisibility was the space where the thread lived and the thread connected Eleanor at her window to Margaret at her desk to the women who washed flags to the women who would wash something else in a factory that had not been built yet to the women who would write reports that would be well-received and filed and forgotten and the thread was continuous and unbroken and invisible and it held the timeline of Hammersmith Grove the way a thread holds fabric and the fabric is the street and the street is the city and the city is the ledger and the ledger is invisible and the numbers are names and the names are the thread and the thread is on Hammersmith Grove and it holds.