At first, it seems obvious a trio is the core cast of Your vice is a locked room and only I have the key (Sergio Martino, 1972): The writer (L. Pistilli), his wife (A. Strindberg) and their young cousin (E. Fenech).
But it's wrong. In fact there are four key characters, if you include the cat. Because the black cat, called "Satan" - that says it all -, is everywhere in the film.
Regular close-ups on his eyes (and later on his unique eye left) are somehow giving a rhythm to the film, almost like an editing device. These sinister snapshots of feline yellow eyes staring in a flash at the viewer efficiently convey a feeling of anxiety and give the strange impression that indeed, the one character which is the puppet master is nobody else but the cat himself -
it must be stressed this is an interesting cinematographic transposition of the black cat's role in Edgar Allan Poe's short novel the film was inspired by.
Now, what if there were five key characters?
What if the cat was double?
Indeed there is one last character we never talked about: the Mother. The mother whose face is the first we see when the film opens on her painting, the mother whose incestuous love for her son stands between him and his wife, the mother whom the cat belongs to...
The mother, absent yet omnipresent, dead yet incredibly alive throughout the film. The mother, watching through the cat's eyes, like spying through a keyhole. The mother, symbolically blinded by his son's wife when she stabs the cat in the eye. And ultimately taking her revenge on her daughter-in-law, at the very last second through Satan's mewing.
Isn't it enough to consider "Your vice" a highly oedipian giallo?
There's definitely more to "Your vice is a locked room..." than meets the eye. Read from this blog here and there. A short article about Giallo & animals can also be found here.