Dr. Lodge is a successful sex therapist who runs a support group for incestuous individuals. His patients include Joyce and Barbara (the magnificent Honey Wilder and Kay Parker, respectively), who we already know have "fooled around" with their own sons. The good doctor must also deal with his own dysfunction. He is a very strict father who has sent his two daughters to boarding school, the eldest of whom (Naomi, a sexy Karen Summer) is caught fornicating in her bedroom. After being expelled from the center, the two sisters return home to discover that their mother (the super-sexy Cyndee Summers) is having an affair with her husband's brother, Billy, and the doctor has kicked her out of home.
The fourth episode of this long-running series does so with a surprising amount of gravitas. Ginger Lynn shines spectacularly as the younger of the two sisters (the other is the even more impressive Karen Summer, always an underrated commodity in genre films) whose family life is shaken when Mom Cyndee Summers, a veteran of the early 1970s, embarks on an affair with John Leslie, the brother of Jamie Gillis, her husband. "Taboo IV" features sensational production values, with a script by Helene Terrie that's meticulously crafted. That's why this is perhaps one of the best adult films of the 1980s, which means it's actually one of the best in the genre.