Septimus Hodge
The brilliant, sarcastic, witty, and womanizing tutor of Thomasina and friend of Lord Byron. He sleeps with Lady Croom and Mrs. Chater but falls in love with Thomasina by the end. It is assumed he is the hermit in the hermitage, working ceaselessly on Thomasina's theories until he dies.
Thomasina Coverly
A brilliant and precocious young woman, Thomasina discovers, although she cannot yet name it, the second law of thermodynamics and chaos theory. She falls in love with Septimus by the end of the play but tragically dies in a fire on the eve of her seventeenth birthday.
Ezra Chater
A relatively untalented poet, Chater desires fame and praise. He convinces himself he is not a cuckold, and allows himself to get involved in a duel with Septimus and to be led to Martinique, where he dies of a monkey bite.
Mrs. Chater
Never seen on stage, Mrs. Chater sleeps with both Septimus and Lord Byron and marries Captain Brice after her husband dies.
Lady Croom
The snobby but libidinous lady of the house, Lady Croom mostly argues with Noakes about her garden being turned into the picturesque and carrying on various affairs.
Captain Brice
Lady Croom's brother who falls in love with Mrs. Chater, taking both her and her husband to Martinique. He marries Mrs. Chater after her husband dies, and sends dahlias back to Sidley Park.
Augustus
Thomasina's snarky and pompous brother who studies at Eton and shows up only to vex his sister and ask Septimus questions about women.
Lord Byron
Never seen on stage, the famed poet and lothario is Septimus's friend and lover to Mrs. Chater. Thomasina admits to a crush on him as well. Bernard assumes Byron killed Chater in a duel and left England because of it, but this is proven to be false.
Jellaby
The Croom's butler.
Bernard Nightingale
A smart but self-absorbed don at a university in Sussex, Bernard explores the connection between Lord Byron and the dead Chater at Sidley Park, and writes an explosive book in which he concludes Byron killed the man over his wife. When this proves to be false, he is humiliated.
Hannah Jarvis
A cool and emotionless biographer of Caroline Lamb, Hannah is studying the hermit of Sidley Park by reading the garden books. Both Gus and Valentine have crushes on her but she eschews relationships. Though more rational than Bernard, her intuition ultimately proves more successful at deciphering the truth of the past.
Valentine
One of the sons of the current Lord Croom, Valentine is a logical and rather glum mathematician studying the grouse population at Sidley Park. He becomes fascinated with Thomasina's equations and comes to see how prescient she was. He has feelings for Hannah.
Chloe
Valentine's younger sister and one of the Croom children, she falls in love with Bernard. While not a scholar she understands how sex complicates the orderly universe.
Gus
The mute and mysterious youngest Croom child, Gus is closest in spirit to the Crooms of the past. He loves Hannah and waltzes with her at the end.
