England at the end of the 18th century.
Married at 17 to the rich and powerful Duke of Devonshire, Georgiana quickly charms high society with her stunning beauty, wit and love of life. However, behind this flamboyant image hides a woman who longs to be loved, a woman deserted by her husband - the only man in the kingdom indifferent to her charms - who prefers her best friend Elizabeth Foster, and who obliges her to accept a ménage à trois.
Unhappy and unsatisfied, Georgiana leads a hectic social life. Her elegance, her extravagance and her taste for gambling create a sensation, particularly when she throws herself into politics alongside the Liberal Party. Spellbound by her energy and charisma, the Whigs' make her their muse. She's celebrated by princes and ministers. And she supports the young Member of Parliament, Charles Grey, with whom she falls passionately in love.