Peccati a Venezia (1983)

Melissa, a beautiful woman in her prime, her cousin Gianni and her elderly and paralyzed Aunt Adele live in a villa in a decadent Venice, Franca, a very young friend of the family comes to the villa. In a short time the life of the three is turned upside down: Melissa, who secretly wants Gianni, cannot bear the fact that he pays attention to the beautiful guest, but even more upset is her aunt, who watches helplessly. Franca also tries to seduce Melissa. One day not tolerating Franca's shameless conduct, Melissa strikes her with a slap, but she remains lifeless on the floor. Convinced of having killed her, she throws her body into the sea with Gianni's help. The commissioner in charge of the investigation immediately understands that something in the story is not right: in reality Franca, sick of heart, died from the fright caused by the sudden break-in in her paralytic and mute aunt's room.