Two years after the events of The Standing Ground, the tiny outpost of Y Tir in North Wales becomes a refuge for those who want to live without implants—permanent links to government surveillance that are threatening to dominate people's lives again. But can Alys, Luke and Emrys thwart the growing threats of the new tech-giants whose offers of enhanced memories and virtual lives mask the erosion of privacy and even humanity?

As new enemies threaten Y Tir's existence, and old enemies emerge to sew seeds of destruction, Alys' and Luke's lives are put under increasing pressure. But there are also allies, not least Alys' and Luke's daughter, Iris, who appears to have fallen out of the mists of Greek legend and into Celtic myth. Can Iris, more strange and powerful even than Myrddin Emrys, also known as Merlin, save the day for Y Tir?