It is ironic that Grace Ansley and Alida Spade return together to Rome, the scene of their surreptitious rivalry. Now, twenty-five years later, it is their daughters who seem to risk "Roman fever" as they are out with aviators while the dowagers sit and gaze at the moonlight. However, in reality, the fever of that visit so long ago has been rekindled. For, beneath the corsets of the ladies from "The Age of Innocence" there pulses jealousy and passion.
In her resentment of Grace Ansley whom she knew was in love with her fiance, Delphin Spade, Alida Spade is now jealous of Barbara, Grace's daughter, who is a beauty with "an edge." Unable to contain her feeling, Mrs. Slade asks Mrs. Ansley "with a touch of asperity" how she and her husband Horace produced a child who is so dynamic. This remark sets memories in motion for both women.
As Mrs. Slade gazes toward the Colosseum she is reminded of how ill Mrs. Ansley became after going out in the night air so many years ago. She makes mention of how damp it was at the Colosseum, but Mrs. Ansley says she does not remember. Finally, Mrs. Slade reveals that she wrote the note that was supposedly from Delphin to Grace Ansley. Dealt a terrible blow, Mrs. Ansley falls to one knee; however, she shocks Mrs. Slade by telling her that she responded to the letter and went to the Colosseum where Delphin then met her.
This time it is Mrs. Spade who suffers from the "Roman fever" when, after remarking that she was married to Delphin for twenty-five years and all Mrs. Ansley had was one night and the letter, and Mrs. Ansley replies, "I had Barbara."