Young Kate Millet is the model for the painting John Singer Sargent is working on in her parents' garden. Everyone says she is posing so well, even though she finds it very hard to stand still. Then one of her father's friends arrives with his two daughters. They're older, taller and have lighter hair than Kate. Sargent decides to use them instead. Kate is devastated.

Based on numerous letters and recollections from the period, Hugh Brewster's story describes Kate's disappointment, the many difficulties experienced by the painter through the long artistic process, Kate's reconciliation with him and how she is immortalized on canvas after all.

Illustrated with over thirty-five of Sargent's paintings and sketches, Carnation, Lily, Lily, Rose recreates the 1880s milieu of the famed American painter during an extended trip to England, and the thoughts and days of a girl who was there alongside him.