What is the full story that neither mrs. slade nor mrs. ansley knows?
The full story that neither Mrs.Slade nor Mrs. Ansley knows is that their husband is seeing both of these women, he is leading a double life unknown to them.
1 Additional Answer
The full story that neither Mrs. Slade nor Mrs. Ansley knows in the book 'Roman Fever' is that Mrs. Slade wrote a letter to Mrs. Ansley asking her to met at the Colosseum. She wrote it as if it was from her then fiance Delphin. She thinks that Mrs. Ansley was stuck waiting for someone who would never show up. What Mrs. Slade didn't know was that Delphin did show up and Mrs. Ansley had an affair with him and got pregnant with his child. Mrs. Ansley didn't know that Mrs. Slade wrote the letter.