Three New York City couples, Bob and Polly, Rod and Linda, Vera and Mark, experiment with drugs and swap mates during one evening of a debauched get-together at one's apartment. In the morning, the three couples leave to go their seperate ways and we see that each couple has sex problems. Vera is a bisexual whom is pregnant and tries to get an abortion. At a local bar, Vera meets and gets picked up by Lee, a lesbian who drugs Vera's drink in order to make her mellow for seduction.
Meanwhile, Linda is revaled to be having an affair with Hank, Rod's brother. After sex, Linda complains to her brother-in-law about her need for a "real man". As for Polly and Bob, her history of lesbian relationships and trysts is revealed when she attends a social transvestitte party where some of the guests are dressed in drag. There, Polly escapes the advances of Rocky, a bisexual man, and returns home. There, Bob rapes Polly when she refuses to have sex with him.
At the climax, the three couples get together again for an LSD party where Rob invites over Bob, a sadist who gets satisfaction by beating women to a bloody pulp. Rob shocks Bob when he makes a sexual pass at him in the bathroom, and Bob retaliates by pushing Rob's head into the toilet. But the party comes to a sudden end when Vera, hallucinating on acid, jumps out an upstairs window to her death on the street below.