During Christmas vacation a mother, daughter and son are turned on by the daughter's older boyfriend. While the mother gets seduced by the boyfriend, brother and sister get it on after they see what is happening between the two. The son thinks his sister is sleeping on the couch and seduces her, then finds out it was his mother. On orgy ensues when the daughter and her boyfriend come in to see what the noise is in the living room. What a Christmas Vacation!