The ledger had been in the drawer for eleven years, and for eleven years nobody had opened it. Maren opened it on a Tuesday because the rain had settled in and there was nothing else in the house she had not already read twice.
The early pages were exactly what she expected. Dates, weather, the hours the lamp had run. Her own handwriting for the last four years of it, before the light went automatic and the island stopped needing anyone to climb the stairs at dusk.
Then, on a page dated a year before she had arrived, a fourth column appeared. It had no heading. It contained a number for every single night, and the numbers never repeated.
What the column was not
It was not the wind. She checked the wind against the harbour records for the same week and found nothing that moved the way the column moved.
It was not the tide, either. The tide has a shape you can recognise from across a room, and the column had no shape at all.
Maren copied out three weeks of it onto the back of a shipping form and put the form in her coat pocket, which is how she came to be standing in the post office two days later, asking a question she had not planned to ask.