When a woman's body is discovered, strangled and bound with rope to the stone torso of Fár Breige, the ancient stone god which stands sentinel above the haunted caves and ancient fortifications of the Atlantic cliffs, the locals believe it was the god who killed her.
In life, Clodagh O'Lochlainn had been a disgrace to her clan, tormenting her former priestly lover, jeering at her husband, robbing her relatives: but could she really have been slaughtered by a vengeful god, as the local population believes? Abandoning preparations for the celebration of her fiftieth birthday, Mara, Brehon of the Burren, with the assistance of Fachtnan and her scholars, takes up the task of solving the murder. Ignoring the ancient legends, she concentrates instead on bringing a mortal killer to justice. But it's only when Fachtnan's small daughter is lost in the labyrinth of passages among the caves that the horrifying truth begins to emerge.