In 1672, London, although women enjoy greater freedom, they are not allowed to practice medicine, a restriction that Hannah Devlin evades by treating patients that most other doctors shun: the city's poor. But Hannah has a special knowledge, and she's drawn into a murder investigation that may conceal a conspiracy as far-reaching as the king himself. She leaves a diary that Claire Donovan, a history teacher at Trinity College, Cambridge in 2008 uses for clues in a modern day murder that appears to relate to events from Hannah's time.