Timeline and Summary

Flamineo begins his creep to the top by facilitating Brachiano's affair with Vittoria. He also messes with Camillo, trying to ruin his plans to get back with Vittoria.
After arguing with his mother over whether it's alright to plot adultery and murder, Flamineo helps the Duke carry out his wicked designs—he breaks Camillo's neck and makes it look like a gymnastics accident. Flamineo is apprehended by the authorities, but not charged with anything.
After Vittoria is sentenced in court, Flamineo escapes suspicion by pretending to be mad.
Joining Vittoria and Brachiano in Padua, after their escape, Flamineo seems to be in the clear. But not really.
He murders his brother Marcello, after Marcello criticizes Flamineo for having a relationship with their maid, Zanche. Brachiano pardons him for the murder, but on the penalty that he needs to have the pardon restored every day, or else he'll be hanged.
The sight of his mother weeping over Marcello's body makes Flamineo feel compassionate (he claims) and apparently somewhat guilty.
After Brachiano's death, Flamineo tries to convince his sister to commit suicide with him—only to reveal it was a plot designed to test her loyalty, after she fires an unloaded gun at him.
But this fake death turns into a real one—Lodovico and Gasparo enter the room and kill Flamineo, Vittoria, and Zanche.