Playwright Norman Krasna adapted his hit Broadway sex farce for the screen under the direction of Peter Tewksbury. Adam Tyler (Cliff Robertson) is an airline pilot who rents a pricey Manhattan apartment and has the weekend off. His prim sister Eileen (Jane Fonda), shows up to visit, complaining that her fiancée Russ (Robert Culp), is pressuring her to have premarital sex, threatening to break up their engagement if she doesn't comply. Adam tells his sister that she is right to resist, that men want to marry women who are virgins, then he leaves with plans to meet his lover, Mona Harris (Jo Morrow), in another city. Left alone, Eileen finds women's lingerie in her brother's closet and realizes that he has a double standard. She leaves, upset. While on a bus, she meets a man named Mike (Rod Taylor). They spend the day sightseeing, fall in love, and return to the apartment after a rainstorm drenches their clothes. Russ and Adam later arrive at the apartment at different intervals. Russ mistakenly believes that Eileen has cheated on him, so he storms out, leaving Eileen with her new love and Adam with plans to marry Jo. Jim Backus has a minor role as a flight dispatcher. Musician Peter Nero, who scored the film, appears in a cameo.