The film revolves around four characters. Helen is an upper class aristo whose family profited from the once thriving colonies. Steve who went to the right schools is having an affair with Helen and likewise is convinced of his superiority. Sybil, daughter of an East End scrap merchant is married to Steve and is intent on revenge. Last but not least is Les, an East End private investigator hired by Sybil to watch Steve and who are now having an affair as well.
The narrative follows Helen and Steve in their bizarre escapades in decadent behaviour from their private parties to their public displays in restaurants and bars. Les and Sybil in hot pursuit and under sheets simultaneously plot Steve's demise and that of the ruling classes.
Decadence is a comedy, a tragedy, a political counterpoint, an alternative view of Thatcher's Britain, laced with a hard hitting but rhythmical dialogue.