Julie and Désirée Clary are courted by the brothers Joseph and Napoleon Bonaparte. Joseph marries Julie and Napoleon is affianced to Désirée. When Napoleon breaks the engagement and marries Joséphine de Beauharnais, Désirée becomes involved with General Bernadotte.
The film is a 125-minute, black-and-white biography of French priest and diplomat Charles Maurice de Talleyrand-Périgord (1754–1838), who served for 50 years under five different French regimes: the Absolute Monarchy, the Revolution, the Consulate, the Empire, and the Constitutional Monarchy. Its title comes from one of the main historical nicknames for Talleyrand, that he shares with demon king Asmodeus and English poet Lord Byron.
Cora Pearl, a demi-mondaine under the Second Empire, falls in love with a legitimist while she is the mistress of Jérôme Bonaparte, the cousin of Napoleon III.
