Martha Strangeways has settled into a quiet life in Strathbran, after the horrific events that traumatised the village a year earlier: her son, Dougie is at university, her friend Orla will give birth at any minute, and she's becoming ever closer to her ex, Jamie.

But all this is turned upside down when her friend at Glasgow CID, DI Derek Summers, calls on her to help with a truly disturbing case: a human ear, with an unusual Celtic earring, has been found next to a railway line in the Highlands.

And when the body of a young woman wearing matching jewellery turns up at a landmark church shortly after, the mystery only deepens. Why has she been laid out in such a ritualistic fashion? Does her trek along the little-known Cailleach Way have anything to do with her demise? And who is running the Facebook Group where she posted details of her journey to the shrine of the Bone Mother goddess?

As Martha tries to unpick the threads, she soon finds herself entwined with a ghost from her own past, and in conflict with the owner of a company committed to a huge hydro-electric scheme that threatens to destroy the goddess's sacred land.

With Halloween approaching, and someone determined to protect the goddess at all costs, can Martha and Summers catch the killer before they strike again – and this time much closer to home…?