The action takes place in 1880 in New Orleans and Saratoga.

On New Orleans' Rampart Street stands a mouldering mansion built twenty years previously by the scion of the aristocratic (and scandalized) Dulaine family for his mistress. Now, in 1880, the daughter of that informal union, Clio (Carol Lawrence), has returned from exile in Paris to "pay back" the Dulaines, who had fiercely rejected her mother. Her picaresque entourage includes her aunt Belle Piquery (Odette Myrtil), Clio's adviser on matters of love; a dwarf coachman-without-coach, Cupide (Tun Tun); and a serving woman Kakou (Carol Brice).

Even greater than her ambition to embarrass the Dulaines is Clio's desire for wealth and status – a husband who is a "catch" – "I'll Be Respectable". To this end, workmen are transforming the house into the showcase it once was – "One Step, Two Step". Later, Kakou and Belle expound upon the finesse a woman must use in finding love – "Gettin' A Man". They decide that love and marriage are two very different things – the latter distinctly a financial consideration.

Clio begins her scandalous rounds in the French Quarter. There she is approached by an emissary of the family who insists she leave the city immediately. Clio dauntingly shows what she thinks of the suggestion by joining the street peddlers in a wildly abandoned dance – "Petticoat High".

One of the spectators is a handsome Westerner, Clint Maroon (Howard Keel). Though he's not quite the man to make that husband she wants, Clio can't resist his attraction, and the two, in separate reverie, wonder how serious they should become. Neither seems what the other wants but "Why Fight This?"

Clint is a gambler, but he has a personal mission. He wants to avenge himself on the railroad magnates who forced his family off their Montana ranch. Clint and Clio decide to pursue their larcenous ways together. But still they wonder about love – A Game of Poker".

Clint joins the Rampart Street ménage and the two devise means of getting the money they will need to move on to greener fields. Belle asks them to accept the love they have and settle down ("Love Held Lightly") but the young adventurers scoff at the notion.

Soon Clio's exploits have become too much for the Dulaines – they settle with her and now Clio and Clint look forward to brighter prospects to conquer – "Saratoga".

At the United States Hotel in the spa city, Clio masquerades as a widowed French countess, Clint as a rich rancher. Clio and Clint are in. The future seems filled with promise – "Countin' Our Chickens". But Clint doubts that he wants anything more than Clio – "You Or No One".

As the second-act curtain rises, the fashionable guests of the hotel are "taking the waters" – "The Cure". Clio has already appropriated the heart of railroad heir Bart Van Steed (Warde Donovan). Clint has met several of his railroad barons – "The Men Who Run the Country". But soon he feels that he and Clio should pull out of their shabby venture. Clio cannot fight her lifelong desire to be "rich and respectable," and Clint Maroon is far from her ideal – "The Man in My Life. Clint embarks on a daring escapade to defend Van Steed's railroad against marauding gangs.

Clio learns of Clint's dangerous expedition just as she is about to accept Van Steed's proposal of marriage. Torn by conflict, she is tearful but undecided. Meanwhile, tiny Cupide longs to go with the gang of toughs but Clint will not permit this. Kakou tries, with tender understanding, to comfort him ("Goose Never Be A Peacock"), but Cupide goes off and joins the flatcars of angry men at the bloody rendezvous. A terrifying fight ensues (represented by a remarkable slow motion ballet by choreographer Ralph Beaumont, a brilliant production high spot). Clint is injured, Cupide almost killed. But their side wins – "The Railroad Fight".

Back in Saratoga, Clio hears news that both Clint and Cupide might have been killed. At last she knows that all she really wanted was Clint. Infuriated by the wealthy poseurs around her, she makes a shocking entrance at a costume ball dressed as a washerwoman. Saratoga society is outraged and Clio is now alone. Suddenly Clint arrives, carrying a battered but living Cupide. He has glanced a blow off the railroaders, and he now owns a healthy chunk of the railroad himself. Clio need never worry again about being "rich and respectable." No idea, motive or misunderstanding can separate their love – and both of them realize that their love is stronger now that they have tested it.