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.

Brussels in the year 1568, as the Flemish people are fighting against the tyranny of the Spanish occupiers. Led by Count de Rysoor, the revolt against the ruthless Duke of Alba, is meant to help Prince William of Orange to get into the city and come to power. Now, the count's lieutenant, has an affair with Elisabeth, Rysoor's wife. For the time being, the count, who thinks of his homeland first, turns a blind eye. But such a relationship might well undermine the whole rebellion movement.

The story of a French officer who is assumed dead during the Napoleonic Wars, but returns ten years later to a very different France, both on a political and personal level. The film is based on the novel Colonel Chabert by Honoré de Balzac.

Taking advantage of their uncle's absence, André and Raymond Rafet organize a New Year's Eve party at his house. The uncle returns unexpectedly, disturbs the party, threatens his nephews to disinherit them and then locks himself in his office. A few minutes later, he is found dead, poisoned.