The address came on a postcard.

No return name. No message. A photograph of the Vistula taken from somewhere north of Płock, and on the back, in pencil, the coordinates of a farm two hours east of Warsaw and a date in October. I didn't recognise the handwriting at first. But I understood what I was looking at.

I had been going back anyway. The Guardian had sent me in for a week, my first time in the zone since the early days, since before any of this, and after years at the Bureau filing the version of the war that fit between the weather and the sport, I had wanted to go in on my own terms and stay long enough to see something true. The postcard did not send me. It only told me where to go once I was there.

I drove out on a Tuesday. The west bank had been retaken that summer and most of the checkpoints there were down, but once I crossed the river the road changed, and there were long stretches where you couldn't tell what year it was, only that no one had cut the verges. Pylons on their sides in the fields. A village with all its doors propped open. A quiet that didn't quite feel empty.

The farm was on a slight rise above what had once been a road. The barn was older than the house. Wooden, sagging at one corner, long past saving and not yet fallen. A woman watched me from the kitchen window as I parked. She did not come out.

Inside the barn it smelled of cold and damp and old hay, and something sweeter I couldn't place. I found what she had left me on a table in the middle of the floor, under a piece of grey canvas, weighted with a brick at each corner, like she had thought about wind.

The notebooks were not under the canvas with the rest. They had been wrapped on their own, in oilcloth, and set on top, four of them, the kind schoolchildren use, the cardboard covers warped with damp at the edges where the wrapping had not quite held. She had protected those before anything else. A person tells you what mattered to them by what they wrap twice. I knew before I opened them that this was the thing, and that the rest, however much there was of it, was the rest.

Under the canvas, then, the body of it. Three binders. A box of cassette tapes and some memory cards. A canvas roll of photographs. And laid across the notebooks, where I would find it first, a manila folder with my name on it in her handwriting, the same deliberate style, slanted forward and underlined twice.

Inside the folder, a single sheet.

Alex. These are the protocols. They are not finished and they were never going to be. Do not come looking for me. Make them public. Tell them what they did. Tell them what we did. D.

I sat down on an old chair and read the first page. Then I went out to the car, brought in the thermos, and read the second. The light through the barn boards moved while I sat.

What she had assembled was not a book. It was a survival. Ten voices, give or take, recorded between the second flood and the second winter. A man called Goya whose mouth never closed around the words he most needed. A girl who had stopped speaking the year her parents were taken. An engineer who could not sit still. A musician who had killed once. Diana had written notes against each transcript in the same pencil she used for everything, small and slanted forward, that was it, sometimes a question, sometimes only a word. True. Hold. Ask again. On a few pages she had written nothing at all.

Between the testimonies she had inserted what she called Protocols. Five of them. Cold documents. Lists, mostly. Maps. The names of streets that no longer existed under names that had not been used since 1944. A taxonomy of factions. A taxonomy of the dead. A pharmacology of the thing they called the Dendron.

When I drove out that evening the woman in the kitchen window was gone. The light was on. I did not knock.

The road to Łuków went on a long time and I drove most of it without seeing it. I had her voice in my head the whole way. The cadence of her notes. The small slanted D. Make them public. Tell them what they did. Tell them what we did.

That is what this book is.

I have changed nothing in the testimonies except the things she asked me to change. The protocols are reproduced as she left them. The order is hers. I have written nothing of my own except what is mine to write, which is this, and what comes between.

Diana Antonoff disappeared from the survivor outpost at Czerniaków on the night of the third flood, in the first January of the occupation's third year. She was twenty-eight years old. She lived alone on an abandoned houseboat moored at Żerań, at the northern edge of the wetlands, where the others said the water ran quietest. She had filed her last dispatch to Suspilne the previous Tuesday. No body was recovered. No statement was issued. The community she had documented filed her name among the missing and went on with the work she had taught them.

Nine months later, the postcard came.

If she is alive, she has chosen not to be found.