Il tuo vizio è una stanza chiusa e solo io ne ho la chiave
Oliviero Rouvigny (Pistilli), a failed writer and an alcoholic, lives in a crumbling mansion with his wife Irina (Strindberg), who is scared of Oliviero's cat, Satan, that used to belong to his late mother. To fight boredom, Oliviero organizes decadent parties for local hippies and humiliates and abuses Irina in front of the guests. After his mistress, a young student, is found murdered, Oliviero becomes the primary suspect. When he finds their maid dead on the premises, he decides to conceal it to avoid further suspicions.
With no-one knowing the identity of the murderer, Oliviero's paranoia builds and leads to more abuse of Irina. Then Oliviero's niece Floriana (Fenech) suddenly arrives for a visit. Irina finds comfort in Floriana's arms and bed, and the two decide to find a way to deal with Oliviero.
After Irina kills Oliviero with scissors, Floriana reveals that she has been after the jewelry that Oliviero had stashed in the mansion. Irina humbly gives her the jewelry and the two part ways. However, Irina also had a plan of her own and she turns to Walter (Ivan Rassimov), the original murderer. Walter kills Floriana and her boyfriend making it look like an accident. Later, Irina pushes Walter off a cliff to have the jewelry all for herself. When Irina returns to the mansion, she finds the police there. An old woman had filed a complaint for animal cruelty, as she had seen Irina stabbing Satan. Inside the mansion, the police officers notice that the cat seems to be mewing in agony inside a wall. As they tear down the wall, they discover the cat and the dead body of Oliviero inside.
cruelty, murder, cult, horror, violence, haunting, flashback, insanity, revenge, storytelling