The Green Dress.

Count Hubert de Latour Latour is the lover of the Duchess de Maulévrier. The day he is surprised by the Duke in the company of his wife and... in a rather compromising situation, Hubert resorts to a subterfuge, claiming that he has come to see the Duchess to seek support to be elected at the Institut de France, whose chairman is precisely her husband. The latter takes him at his word and Hubert becomes... a member of the French Academy! Which just shows that everything leads to everything.