Act One is a fictionalized account of the period in George Seurat's life when he was painting A Sunday Afternoon on the Island of La Grande Jatte. This act covers two years, taking place on a series of Sundays during which George and his mistress, Dot, part ways, even though they've had a child together. The other major characters, most of whom George includes as figures in the painting, are his mother; his mother's nurse; Jules, another painter who, unlike George, is commercially successful; Jules's wife, Yvonne, and their child, Louise; Jules and Yvonne's servants, Franz and Frieda; an anti-social boatman; two shopgirls, both named Celeste; a Soldier and his mute friend, also a soldier, who flirt with the girls; Louis, a baker, whom Dot marries after she breaks up with George; and a wealthy American couple, from Charleston, South Caroline, referred to merely as Mr. and Mrs., who are visiting Paris.
Mr. and Mrs find they have a taste for the pastries that Louis bakes and they hire him to return with them to Charleston and work for them there as their baker. At the end of the act, as Dot is preparing to leave for America with Louis and Marie (her daughter by George), George finally completes the painting.
Act Two jumps to America 100 years later, focusing on George and Dot's great-grandson, also an artist named George, who is suffering an artistic crisis. Unlike his great-grandfather, this George is a commercially successful artist, getting many commissions for work that he finds increasingly unfulfilling. George's only living relative seems to be his grandmother, Marie.
George presents his latest "invention," a color-and-light machine called Chromolume #7 (the seventh in a series of similar machines), at a special event at the Art Institute of Chicago, the museum where his great-grandfather's masterpiece, A Sunday Afternoon on the Island of La Grande Jatte, is housed. The work is a homage to the painting. Marie accompanies him to the event and tries to counsel him in his crisis. George finds it difficult to believe Marie's insistence that her real father was Seurat and that he is therefore Seurat's great-grandson.
George is invited by the French government to present Chromolume #7 on the island of La Grande Jatte. Marie is to accompany him to Paris, but she dies before the trip. Alone on the island, George is visited by the spirit of Dot, who believes he is her George, and then by the figures in the painting, who acknowledge him for giving them immortality through the painting. He realizes that he is truly connected with his great-grandfather and finds the courage to move beyond his crisis of belief in his work and to create new art in his own voice.