Arcadia is set in Sidley Park, an English country house in Derbyshire, and takes place in both 1809/1812 and the present day (1993 in the original production). The activities of two modern scholars and the house’s current residents are juxtaposed with those of the people who lived there in the earlier period.

In 1809, Thomasina Coverly, the daughter of the house, is a precocious teenager with ideas about mathematics, nature and physics well ahead of her time. She studies with her tutor Septimus Hodge, a friend of Lord Byron (an unseen guest in the house). In the present, writer Hannah Jarvis and literature professor Bernard Nightingale converge on the house: she is investigating a hermit who once lived on the grounds; he is researching a mysterious chapter in the life of Byron. As their studies unfold – with the help of Valentine Coverly, a post-graduate student in mathematical biology – the truth about what happened in Thomasina’s time is gradually revealed.

The 13-year-old (later 16-year-old) daughter of Lord and Lady Croom, Thomasina is a precocious genius. She comes to understand chaos theory and the second law of thermodynamics, before either is established in the mathematical and scientific communities. Stoppard “apparently based”the character on Lord Byron’s daughter Ada Lovelace (Augusta Ada King, Countess of Lovelace). She was an English mathematician who conceptualised how Charles Babbage’s Analytical engine could be used, foreseeing the binary computer.