Boys' Night Out (1962)

Fred, George, Doug and Howie are quickly reaching middle-age. Three of them are married, only Fred is still a bachelor. They want something different than their ordinary marriages, children and TV-dinners. In secret, they get themselves an apartment with a beautiful young woman, Kathy, for romantic rendezvous. But Kathy does not tell them that she is a sociology student researching the sexual life of the white middle-class male.