I'm confused about Simon's role in this plot (SPOILERS!)
Aside from the murder of the four teenagers, I'm not sure what Simon's role is in the murder plot. The way I understood it, Ventura planned the murder of the Countess because she wouldn't sell her land to him. Ventura got his lady friend (Laura?) involved and sent her to seduce Donati, the Countess's husband. Apparently Laura convinced Donati to murder the Countess.
But then what? Was it Simon who came out of the shadows and murdered Donati? And if so, why would he stand by and watch his own mother be garroted? If he cared about his mother enough that he would want revenge on her murderer, then why would he be a part of a scheme to kill her in the first place? And if he didn't know she was going to be murdered, why was he lurking there waiting to kill Donati in the first place?
Ventura had Simon in on the whole conspiracy from the beginning, since there was that scene in the boat house where they exchanged money, so Simon knew about Ventura's intentions. But when Laura confronts Simon in the boat house near the end of the film, he gets angry at her and she blames the Countess's murder on Ventura. Can someone clue me in to what I'm missing here?