Piccoli again plays a lonely, calculating professional who comes to plot a crime, though the similarities end there. Max was cold and emotionally distant; Simon Léotard, as the title character notes, wants to be loved by everyone. A modestly successful investor, Léotard has devoted his life to the family business, enjoying the camaraderie of his partners as well as the respect (and occasional favors) of district judges. He may have only experienced emotional intimacy with high-priced mistresses, but that's better than nothing, and staying single has given him more time to work.
Léotard finds his business—and by extension his life—in jeopardy when his partner commits suicide and leaves behind a mountain of debt. Evidently the partner had been set up by a shady rival who bankrupts other businessmen in order to take control of their properties. Léotard wants to get even, but he doesn't want to stoop to the level of his rival; unfortunately, he learns, he can't do both. Mado follows this character as he regains control of his business and relinquishes his only principles, consorting with criminals and blackmailing his foes.
In summary the movie sounds like a Chabrolian tale of upper-class hypocrisy, but it doesn't feel as pointed as a thematically similar Chabrol work like The Unfaithful Wife or Une Partie de Plaisir. Sautet often digresses to consider the supporting characters—such as a young accountant (Jacques Dutronc) who helps with Léotard's messy finances and the accountant's hippie-ish friend, who's determined to manage property in the countryside—so that the main storyline feels like part of a larger web. Writing about Mado in the Reader, Sautet skeptic Dave Kehr described the director's "track-and-zoom style" as "close to being ugly" while acknowledging that "it makes a perfect accompaniment to his rambling plot, picking insights out of apparent chaos." As I see it, this chaos is life itself, which hovers constantly just outside the frame of Sautet's camera, threatening to destabilize the familiar order of narrative cinema.