NAKED CAME THE STRANGER (Radley Metzger, 1975): The Costume Party Scene
This is the softcore version of the Costume Party scene in Radley Metzger's 1975 film "Naked Came the Stranger", where Jilly (Darby Lloyd Raines) and Billy (Levi Richards) go to a merry costume party, where Billy meets his mistress (Mary Stuart) and Jilly plans to have affairs with her friends Marvin (Alan Marlow) and Craig (Gerald Grant).