In the car on the 15, before anything had happened, before Margaret had said a word about her suspicions to anybody, her granddaughter said Nathan’s scared — and she used his name, which she had never once used, and which she has never used since.

The second is smaller and worse.

Sophie has never been able to say why she knew it was the left side.

Margaret is a nurse.

She is sixty-five now and she has spent her whole adult life inside a framework that does not have room for the other explanation, and she is not going to abandon it at this stage.

But she stopped, some years ago, requiring her granddaughter to choose.