Mary spies on her step-brother's girlfriend, Nina, and finds out she is cheating on him! Nina is on the phone and flirting with another guy than her boyfriend. Little does she know that Mary, her boyfriend's little step-sister, is lurking behind the couch where she listens to the whole thing! Mary interrupts the phone call by coming up from behind the couch to confront Nina. Nina tries to talk her way out of it, but there is no explanation that is gonna be good enough to change anything at all! Mary is so appalled by the slutty behavior from her step-brother's cheating girlfriend that she decides to teach her a lesson that involves tying up and gagging the whore before she tells her step-brother all about what a cunt Nina is!!!