In 1972 Los Angeles, film screenwriter Billy Waters lives in Hollywood with his wife Sheree Sudaine, a British actress who stars in several of his films, and their fifteen-year-old daughter Junior. Billy is burdened by the demands of his wife, while Sheree regularly argues with her daughter. Despite being father and daughter, Billy and Junior are sexually attracted to each other; while Junior constantly flirts with her father, Billy keeps his incestuous urges to himself. Their neighbor Lou Jean, meanwhile, is attracted to both Billy and Sheree, especially after encountering them during a party held by her brother Artie where Billy kissed her.
Sheree taunts Billy over his reliance on her acting in his films, as well as his obvious attraction towards his own daughter. Junior makes out with her French tutor Charlie after a lesson. Charlie narrates a bizarre story of his uncle going to heaven and, disgusted by seeing sexually immoral acts on earth, gets an angel\\\'s help to change people\\\'s sex drives into them having handshakes instead. After his story ends, Charlie and Junior decide to have sex, with Charlie teaching her fellatio.
While having a champagne bath together, Billy and Sheree reminisce when Billy first had sex with the then-fifteen-year-old Sheree for the first time, which got her pregnant with Junior and led to their marriage. Sheree once again teases him about his attraction towards Junior as well as Lou Jean taking a liking towards Billy, but Billy later questions if Sheree also likes Lou Jean. Sheree denies being a lesbian while Billy asserts that he will remain faithful to her. However, both of them eventually admit they are attracted to Lou Jean. Sheree talks about catching Junior and Charlie about to have sex in a prior session.
Billy walks in on Charlie and Junior making out, causing Charlie to quickly escape the premises. Junior, still topless, uses the moment to try to seduce her father, while Billy reiterates that as her father he only sees her as his child, and that he is loyal to his wife. Sheree reminds him of when they kissed romantically; Billy reminds her that he was drunk and thought she was Sheree. Junior then says that if she cannot have him, then she can move on to the significantly older Sir Harry, a wealthy socialite pushing sixty who had recently separated from his fifth wife and kissed Junior during a party. To prove he does love her, Billy takes Junior to a big night out into town. When they arrive home, Billy continuously rebuffs his daughter\\\'s proposals to have sex and the two simply drink instead.
Meanwhile, Sheree visits Lou Jean and takes a swim with her. The two enjoy themselves and eventually kiss. Lou Jean tearfully confesses a time when her stepmother and her ex-boyfriends drugged and raped her until her father and brother arrived in the nick of time, causing her stepmother and her fellow rapists to flee but resulting in her lifelong fear of being touched and groped by men. She shares that Billy was the only man who wasn\\\'t \\\"grabbing\\\" her hence she fell in love with him. Sheree comforts Lou Jean.
Junior changes into provocative lingerie and enters her father\\\'s bed where she begins kissing a half-asleep Billy, who believes he is kissing Sheree. Sheree arrives home to find her husband and their daughter making out, and she forcefully pulls out Junior, who flees to her room. Sheree angrily confronts Billy and does not believe his story that he was unaware that he was making love to Junior. Sheree forces Billy to move out and calls Lou Jean to move in as both her lover and Junior\\\'s new tutor. She chastises Billy for spoiling Junior all these years and takes it upon herself to discipline their daughter.
The next morning, Lou Jean arrives and she and Sheree find that Junior has fled home. Billy is informed of Junior being missing and calls the police. After Sheree cries about Junior in Lou Jean\\\'s arms, the two have sex. Billy arrives home and catches the two in bed, and Sheree invites him in bed to have sex with the two of them. Junior returns home and catches the three in bed making love. Junior declares that, having been ultimately rejected by her father, she had moved in with Sir Harry as his new lover and is at home to pick up her valuables before she bids her parents farewell. With Junior no longer needing assistance, Lou Jean leaves as well, having realized being lovers with both Billy and Sheree has been too much for her and desiring a traditional relationship instead. After saying goodbye, Lou Jean tearfully picks up her belongings and leaves.
