The House on the Lough. Tide House Mysteries, #6

They thought the edge of the world was a good place to lose a child. A letter comes out of Donegal: fifty years of a family's record, kept on a lough at the last parish before America. Maya Anders follows it to the wild northwest of Ireland - and to a truth that reaches all the way back to where the whole of it began, and proves the machine was never one country's. It was one design, planted at every edge of the world at once.
The sixth and final Tide House Mystery - the record endures.