Flavia de Luce is eleven years old, one of three motherless sisters living in 1950s England. She takes an extreme interest in chemistry--especially poisons--and fortunately is in possession of her Uncle Tar's laboratory where she can make use of the information she discovers. In the first three books she deals with a corpse in the cucumber patch, cruel pranks by her older sisters, and gets involved in mysteries involving old murder investigations, puppet theaters, and gypsies.
The fourth book, the title taken from the poem The Lady of Shalott, takes place just before Christmas. Money has gotten so tight that Flavia's father has rented Buckshaw, their family home, to a film company. Meanwhile, Flavia has reached the age where she is not so sure that Father Christmas is real and has formulated a plan to prove his existence once and for all.