The main conflict in "Roman Fever" is between Mrs. Slade and Mrs. Ansley over Delphin Slade. When the two women were young they were both in love with the same man, even though he was engaged to Alida, Mrs. Slade. The story takes us back to a winter the two women spent in Rome.
Mrs. Ansley was in love with Delphin Slade and Alida thought she was going to try to steal him away from her. So she sets up a rouse, writing a phony letter to Grace, Mrs. Ansley, from Delphin, but the letter was really written by Alida, Mrs. Slade.
Grace, Mrs. Ansley, actually responded to the letter, writing to Delphin Slade, who arranged for the two of them to be let into the Collesium. Mrs. Slade did not know about this, and she accuses her of lying. The twist to the story is that Mrs. Ansley's daughter, Barbara, is actually Mr. Slade's daughter.
Alida married Delphin Slade as planned, but Mrs. Ansley, who had a brief affair with him, had his daughter.