It is acknowledged that Edgar Poe's short novel "The black cat" was a source of inspiration for Martino/Gastaldi's Your vice is a locked room and only I have the key (1972).
However it must be said that the film was also strongly influenced by Henri-Georges Clouzot's chef-d'oeuvre Les Diaboliques (1955).
Both movies involve a twisted trio: a domestic tyran (Delassalle/Ruvigny), his wife with a weak condition (Christina/Irina) and a cold-blooded lover (Nicole/Floriana).
Both take place in a run-down school/manor which reinforces the feeling of a decadent atmosphere.
Both also build on a similar plot, where the two women team up to get rid of the evil man. But things are not what they seem, and the frontiers between good and evil are ever changing in the tension of a cynical role play.
Sergio Martino & Ernesto Gastaldi even 'cited' Clouzot directly in a few different scenes : the wife humiliated and forced to eat/drink something disgusting in public, a dead person's clothes delivered back by the dry-cleaner.
And above all the famous scene where the terrified wife hears Delassalle/Ruvigny's typewriter working when the man is supposed to be dead.
In the night, as the door frighteningly opens in a creepy sound on an empty room with the typewriter on the desk, the camera slowly enters and reveals what was written on the white pages which cover up the table. Somebody typed the same thing over and over: the name "Michel Delassalle" in 'les Diaboliques', and, as a if Gastaldi & Martino had wanted to pay a witty tribute to Clouzot, the word "Vendetta" (Revenge) in 'Your Vice'.
When you finally get to discover both films' twist endings, this idea of "vendetta" makes complete sense: indeed, in Your vice, one of the characters takes a revenge on what happened in Les Diaboliques.
Read more about Clouzot's "Les Diaboliques" here, and have a look at a few screenshots there. Henri-Georges Clouzot (1907-1977) is a great French director who deserves a closer look: read this article from "Senses of Cinema".