The protagonists are Grace Ansley and Alida Slade, two middle-aged American women who are visiting Rome with their daughters, Barbara Ansley and Jenny Slade. The elder women grew up in Manhattan, New York, and were friends from childhood. A youthful and romantic rivalry led Mrs. Slade to nurture feelings of jealousy and hatred against Mrs. Ansley.
In the opening pages of the story, the two women compare their daughters and reflect on each other's lives. Eventually, Mrs. Slade reveals a secret about a letter written to Mrs. Ansley on a visit to Rome many years ago. The letter was purportedly from Mrs. Slade's fiancé, Delphin, inviting Mrs. Ansley to a rendezvous at the Colosseum. In fact, Mrs. Slade herself had written the letter, in an attempt to get Mrs. Ansley out of the way of the engagement by disappointing her with Delphin's absence (and, it is implied, to get Mrs. Ansley sick with Roman Fever). Mrs. Ansley is upset at this revelation, but reveals that she was not left alone at the Colosseum—she responded to the letter, and Delphin arrived to meet her. Mrs. Slade eventually states that Mrs. Ansley ought not to feel sorry for her, because "I had [Delphin] for twenty-five years" while Mrs. Ansleyhad "nothing but a letter he didn't write." Mrs. Ansley responds, in the last sentence of the story, "I had Barbara."