Mireille explained the cipher to herself before she explained it to anybody else, because the explaining was how she kept her hands from shaking. She had done it every night since the autumn, in the cold rooms of the Chancery’s audit house at Sallowmere, and every night the explanation had come out a little more exact, as a column becomes more exact the longer one stares at it. She did it now, sitting on the edge of the bed in the room over the bakehouse with the ledger on her knees and the lamp turned low, and she did not allow herself to skip a line.
Each letter of a note was taken from a page number of the Census. Then the letter was taken from a line on that page, counting from the head of the leaf. Then the letter was taken from the name of a struck village, by its position in the column, so that the same note could not be read from any two places in the book. The first letter was the page. The second was the line. The third was a name, and a name could be broken on any letter of its length, so the cipher was never quite the same twice. It was an accountant’s joke and a witness’s precaution, and she had been rather proud of it the night she thought of it.
