Dr Ruth Galloway is in her late 30s. When she's not digging up bones or other ancient objects, she lectures at a university in Norfolk. She lives, alone but happily so, in a bleak, marshy area called Saltmarsh overlooking the sea and Norfolk's vast skies with her cats and Radio 4 for company. She's a salty character — quirky. When a child's bones are found in the marshes, near a dig that Ruth and her former boyfriend Peter worked on ten years before, Ruth is called upon to date them. They turn out to be bronze-age bones and DCI Harry Nelson, who called on Ruth for help, is disappointed. He had hoped they would be the bones of a child called Lucy who's been missing, presumed dead, for ten years. He has been getting letters about her ever since — odd letters with references to ritual and sacrifice, and including quotes from the Bible and Shakespeare. Then a second girl goes missing and Nelson gets another letter — like the ones about Lucy. Is it the same killer? Is it a ritual murder, linked in some way to the site near Ruth's remote home? Then one of Ruth's cats is killed and clearly she's in danger from a killer who knows that her expert knowledge is being used to help the police with their enquiries.