Servais Mont (by Fabio Testi), a photographer, meets Nadine Chevalier (by Romy Schneider), an actress who earns her money starring in cheap soft-core movies. Falling in love with her, he borrows money from the loan sharks to finance the theatrical production of Richard III and gives Nadine a part. Meanwhile, Nadine is torn apart between Servais and her husband Jacques (by Jacques Dutronc), to whom she has moral obligations. That Most Important Thing: Love is an explosive melodrama, that explores the tension between passion and duty, as well as between art and trash.