Advertising executive Bill Compton, his wife Joan, and daughter Melissa are a wealthy family living in New York’s Upper East Side. Melissa has been living with her drug-dealing boyfriend. After Melissa overdoses and is sent to a hospital, Compton goes to her boyfriend’s apartment to get her clothes. He confronts and kills the boyfriend in a fit of rage. At a nearby bar he hears factory worker Joe Curran ranting about how he hates hippies, and Compton blurts out that he just killed one. Joe reacts favorably, but Compton says it was a joke.
A few days later, Joe sees a news report about a drug dealer found slain a few blocks from the bar. He calls Compton and meets him. At first Compton is wary that Joe may be attempting blackmail, but Joe assures him that he admires Compton for killing the drug dealer. They become friends, and Compton and his wife have dinner at Joe’s house with his wife. Melissa escapes from the hospital and returns to the family apartment, where she overhears her father discussing the murder. She storms out of the apartment house, saying to Compton, “What are you gonna do, kill me too?” Compton tries to restrain her, but she breaks away.
Joe and Compton search for her, and meet a group of hippies at a bar in downtown Manhattan. They join the hippies at an apartment, where the hippies share their drugs and girlfriends with the pair. They then abscond with drugs brought by Compton, which he had taken from the drug dealer, as well as Joe’s and Compton’s wallets. Joe beats one of the girls until she tells him that their boyfriends often spend time in an upstate commune. Joe and Compton drive to that commune, with Joe bringing rifles. In a confrontation at the commune, Joe and Compton kill all the hippies there, and Compton unwittingly kills his own daughter.