Taking its cue from Luigi Comencini's 1974 art-house hit "Mio Dio, Come
Sono Caduta In Basso" (a/k/a "Till Marriage Do Us Part"),* this porno
period piece is one of the more ambitious adult films on record.
*snip*
* http://www.imdb.com/title/tt0071844/combined
The Marquise Eugenia di Maqueda, an orphan raised by the nuns, marries
Raimondo Corrao, but on their wedding night she finds out that he is her
brother. The piece of news is in a letter written from Paris by their
father, a womaniser who lives and hides from them in the French
headtown. The pair decide, to avoid the scandal, to live as brother and
sister. He will later leave for the war in Lybia, she will find solace
and sexual satisfaction in the arms of the family chauffeur.