Barbara Nickerson and her upper-class boyfriend Josh Bickford are surprised at friend Stan Osgood's house when Twig Webster and his ill-mannered friends crash a private party there. Josh is appalled by Twig's behavior, but Barbara seems attracted to his animal magnetism.
Josh's conservative parents are concerned over his future. Twig, meanwhile, has an alcoholic mother, Hazel, who is abusive toward his father. At a party for adults, Twig finds his mother in a compromising position with another man. When they argue, she falls down a flight of stairs.
Twig becomes out of control, beating up Barbara, then also striking Josh when he tries to come to the girl's rescue. Barbara ends up hospitalized. Upon seeing their son's grief and also learning that Hazel has died, the Bickfords vow to become better parents to Josh.