The function requires a number of inputs. One of these is a date. Azure is a system for generating one-time pads that change every day, and circumstantial evidence from the room of the dead abacus slaves tells him that, at the moment of their death, they were working on the one time pad for 6 August 1945, which is four months in the future. Waterhouse writes it down in the European style (day of the month first, then month) as 06081945, then lops off the leading zero to get 6,081,945—a pure quantity, an integer, unmarred by decimal point, rounding error, or any of the other compromises so abhorrent to number theorists. He uses this as one of the inputs to the zeta function. The zeta function requires a few other inputs too, which the person who designed this cryptosystem (presumably Rudy) was at liberty to choose. Surmising which inputs Rudy used has occupied much of Waterhouse’s thoughts in the last week. He puts in the numbers he has guessed, anyway, which is a matter of converting them to binary notation and then physically incarnating those ones and zeros on a neat row of stainless-steel toggle switches: down for zero, up for one.