In 1553 Catherine lives in Coity Castle in Wales. She is a young girl, well looked after, highly educated but has no family and no knowledge of her background.
The same year, a young Maori girl, Mihingarangi undertakes a long walk across an island off the coast of New Zealand with a special purpose in mind.
In 2024 Dr Phryne Howard arrives in New Zealand for a sabbatical, running away from the pressures put upon her by a major American pharmaceutical company.
When Phryne unexpectedly receives Catherine's diary and her notebooks, she starts to notice parallels in both of their lives; an interest in herbs and native remedies, and the way both their lives have been manipulated by people unknown to them. An encounter with an ancestor of Mihingarangi leads Phryne to investigate the healing properties of a rare seaweed and how this could benefit the local tribe however she has a strong compulsion to discover who Catherine is and with the help of a local author she embarks on research which leads to some startling conclusions