When Cora and her younger sister, Mimi, are sent to stay with their great Auntie Ida in an isolated village in 1958, they discover that they are in danger from a centuries-old evil and, along with village boys Roger and Peter, strive to uncover the horrifying truth before it is too late.

Eleven-year-old Flavia de Luce, an aspiring chemist with a passion for poison, must exonerate her father of murder. Armed with more than enough knowledge to tie two distant deaths together and examine new suspects, she begins a search that will lead her all the way to the King of England himself.