Questions arise in our minds as the last line of this astonishing story sinks into our consciousness. I believe no one would blame us for wondering how much Delphin Slade really hid from his widow and former mistress.
Despite the women's confessions, it can be argued that neither Mrs. Alida Slade or Mrs. Grace Ansley know the full story of their past. In the story, Alida exults over the fact that she was the woman Delphin chose to share his wealth and sexual energy with. Unbeknownst to Mrs. Slade, Grace has cherished her own dark secret for two decades: her daughter, Barbara, is actually Delphin Slade's progeny.
Delphin Slade had an affair with Mrs. Ansley while engaged to Mrs. Slade decades ago. The story does not reveal Delphin's past thoughts or motives at all. In fact, when the story begins, Delphin has been deceased for a time. His ghost, however, hovers menacingly over the plot.
We learn that Mrs. Slade set a trap for Mrs. Ansley decades ago. She wrote a letter inviting Mrs. Ansley to meet at the Coliseum and signed it in Delphin's name. Alida's motive was to be rid of Grace. Knowing that her rival had delicate health, Mrs. Slade arranged for an evening rendezvous in the dank Coliseum. She hoped that Grace would succumb to the Roman fever, an often fatal illness. For her part, Grace answered the letter and met with Delphin. The result of the encounter was Barbara.
Interestingly, Wharton does not tell us whether Delphin knew about the letter writer's identity. It is unclear whether he harbored any suspicions at all, and there is no evidence that he revealed his theories to either woman. It is conceivable that Delphin not only knew the letter writer's identity but that he also chose to hide his suspicions from Alida and Grace. Additionally, although the story does not indicate it, Delphin may have also known that Barbara was his child.
We can reasonably conclude that Delphin never acknowledged Barbara as his own during his lifetime. Why? The last line of the story tells us that Grace kept her secret well. However, the text strongly hints that Delphin took his own secrets to his grave. It is apparent that neither Grace nor Alida know the full story of their past.