Don has an affair with a new salesgirl, Dusty (Jordana Brewster).
When Don confesses the situation to Mona, she doesn't file for divorce. Instead, she methodically insists that Don must kill Dusty to protect their family's reputation and "perfect" life.
Delivers a standout performance as a "Stepford Wife" gone sociopathic. Her cold, detached demeanor provides the film's most effective dark humor.