The letter arrived on a Tuesday in late November, which Marta noticed because she still kept the tide tables and Tuesday was a day of large differentials. She found it wedged behind the gas bill, handwritten on cream paper with a German postmark — Frankfurt, the stamp said, though the return address was a P.O. box she didn't recognise.
She stood at the kitchen window with it for a long time before she opened it.
The handwriting was Erik's. She was sure of this in the way she was sure of very few things: the particular slope of the capital M, the way the letters in his name — he had signed it, at the bottom, simply Erik — tilted very slightly to the right, as if they were walking into wind. She had known that handwriting for thirty-one years. She had watched it change, gradually, into something more constrained and careful as his hands began to trouble him. But this was the earlier version. The version from before.
Erik had been dead for four years.
She had retired from the Hydrographic Service eleven years ago, after thirty-two years of survey work along the Baltic coast. She had measured tidal ranges in Finland and Estonia, supervised the re-charting of three contested shipping lanes, and spent six months on a research vessel in the Kattegat that she still thought of as the best six months of her professional life. She was not a superstitious person. She believed in measurement, in the reliability of instrumentation carefully maintained, in the slow accumulation of accurate data. The sea was not mysterious to her. It was subject to forces she understood: gravitational pull, atmospheric pressure, the geometry of basins.
She sat down at the kitchen table and read the letter twice.
It said: Marta, I know this will seem impossible. I am not going to ask you to believe it yet. I am going to ask you to come to the address below on the twenty-third. If I am wrong about everything, you will have spent a day travelling for nothing. I have been wrong before. But I don't think I am wrong about this. — Erik.
There was an address below. Weidengasse 14, Frankfurt. No apartment number.
She called her daughter, who said: Mama, don't go.
She called her former colleague Sten, who had worked alongside Erik for fifteen years and whose opinion she trusted more than almost anyone's. Sten said he didn't know what to say, which she took as a kind of answer.
She looked up the address on a map. It was in a quiet residential quarter of Sachsenhausen, near the river. The street existed. Number fourteen existed. In the satellite view it appeared to be a narrow townhouse, three storeys, with a green door and window boxes that she couldn't quite make out.
She closed the laptop and went to bed.
At 3 a.m. she got up and made tea and sat with the tide tables for the coming month, running her finger down the columns. High water, low water, the range between them. On the twenty-third: a spring tide. Difference of 1.7 metres at the nearest gauge, which was only an approximation — the real figure depended on the wind.
She booked a train for the twenty-second.
The house had a blue door, not green — the satellite image had been wrong, or the paint had changed. She stood on the pavement for several minutes before ringing the bell. The street was very quiet. A woman walked past with a pushchair and didn't look at her.
The person who answered the door was not Erik.
He was about sixty, with short grey hair and a careful, watchful expression she recognised from people who had spent long periods in difficult conditions. He said her name. She said: Where is he?
He said: Please come in.
The house smelled of coffee and old paper. There were maps on the walls — not decorative prints but working charts, annotated in pencil, with the particular density of information that distinguished charts made for use from charts made for display. She stopped in front of one. It showed a stretch of coastline she knew well: the outer islands of the Danish archipelago, south of Fyn. The pencil marks were in a hand she recognised.
She turned around.
The grey-haired man was watching her from the doorway to the kitchen. He said: He left them for you. In case you came. He said you would know them.
She said: Where is he now?
There was a pause she recognised as the kind people make when they are deciding how much of the truth to use.
He said: He was here until three weeks ago. Then he was gone again. That's the most accurate thing I can tell you. He asked me to give you the charts and to say that the measurements were correct. He was very specific about that. He said: tell her the measurements were correct.
She looked at the charts again. There were seven of them. Each one covered a different section of the same stretch of coastline, with pencilled annotations in the margin that she now saw were not compass bearings or depth soundings. They were dates. And figures. And beside each figure, a small notation she had invented herself, thirty years ago, in a field notebook — a shorthand for a specific type of tidal irregularity that she had never published and had never shown to anyone except Erik.
She said: Can I sit down?
The grey-haired man brought coffee. She spread the charts on the table and began to read them the way she had always read charts: from the edges inward, from the known toward the uncertain. Outside, the November light was going. The river was somewhere nearby; she couldn't hear it but she could feel it the way she always felt water — as a kind of pressure in the room, a weight in the air that had a direction.
By the time she finished reading it was fully dark.
She sat for a while without speaking. Then she said: He found it.
The grey-haired man nodded.
She said: After forty years.
He said: He wanted you to know. He was very clear about that. Whatever else, he wanted you to know that.
She rolled the charts carefully, the way she had been taught to handle charts that mattered, and put them in her bag. She thanked the man, whose name she still didn't know and didn't ask. She walked back to the station in the dark along the river, and the water moved alongside her in the way it always had — indifferent, continuous, subject to forces she had spent her life measuring.
On the train home she held her bag on her lap with both hands and watched the lights of the suburbs give way to darkness and then to fields, and she thought: forty years. She thought: the measurements were correct.
She thought: I always knew they would be.