Édouard Molinaro's La Cage Aux Folles is an adaptation of a play of the same name by Jean Poiret in 1973, which in turn was inspired by Charles's Dyer's Staircase (1966).
Renato (Ugo Tognazzi) and Albin (Michel Serrault) are a homosexual couple who run the drag cabaret La Cage Aux Folles, and in fact live in the same building. Albin shows openly camp behaviour, the flat is full of camp signs, such as Greek statues, a pot shaped as a pair of buttocks, etc. Renato has a son, Laurent (Rémi Laurent), from a brief relationship with a woman and the problem is that Laurent wants to marry Andréa Charrier (Luisa Maneri), the daughter of the ultra straight-laced Simon (Michel Galabru) and Louise (Carmen Scarpitta). Obviously Andréa's parents want to meet Laurent's parents, but another problem is that Simon is député of an ultra-conservative political party.
So Renato has to hide certain incriminating objects, although he's still reluctant to hide Albin away while the future parents-in-law are there. He contacts his previous lover Simone (Claire Maurier) to pose as his husband. In the end the worst happens and Albin turns up for the occasion dressed as a woman, and the future in-laws are naturally shocked by this turn of events. When Simone turns up and Albin's wig is off they soon discover the truth. Meanwhile, journalists outside are waiting for a scoop.
Charrier sees his career in ruins if they leaves by the front of La Cage Aux Folles, although Albin's plan is to dress the Charriers in cabaret, which they do and the marriage takes place.
Obviously a farce resting on disguise, hackneyed stereotyping and gags which today would probably be unacceptable, but interesting as a period piece.