The novel takes place in the English countryside in 1950. Flavia de Luce, the story’s 11-year-old narrator, is tied up and locked in a closet by her older sisters, Daphne (Daffy) and Ophelia (Feely). Flavia is adept at freeing her hands and gagged mouth and picking locks, so she frees herself and joins her father at the dinner table.

Flavia belongs to an old aristocratic British family, and the Buckshaw estate has been their home for centuries. Her mother is deceased, “killed in a mountaineering accident” when Flavia was one and now “not often spoken of at Buckshaw” (4). Flavia and her sisters rarely see their father, Colonel Haviland (Laurence) de Luce, as he spends all his time in his study with his beloved stamp collection.

Flavia’s great-uncle Tarquin de Luce was a chemical genius, so there is an elaborate laboratory in the house, which is Flavia’s sanctuary. She has loved chemistry since the day she found An Elementary Study of Chemistry, which belonged to her mother. Flavia quickly became a prodigy in the subject and enjoys recreating the experiments found in the books in the laboratory. She notes, “My particular passion was poison” (10).