In 1814, after 20 years of military glory Napoleon Bonaparte, the Emperor of France, faces defeat at hands of the sixth coalition, the forces of Britain, Austria, Prussia and Russia. Facing certain defeat, Napoleon's marshals gather and demand that he abdicate. At first Napoleon violently refuses, but after hearing of the surrender of his last army he agrees.
In 1807, during the Napoleonic Wars, British Royal Navy Captain Horatio Hornblower (Gregory Peck) commands the 38-gun frigate HMS Lydia on a lengthy secret mission to Central America. He is to provide arms and support to a megalomaniac named Don Julian Alvarado, who is calling himself "El Supremo" or "The Almighty" (Alec Mango), in his rebellion against Spain, an ally of Britain's enemy France. As Hornblower observes to First Lieutenant Bush (Robert Beatty), "War breeds strange allies."
The film begins in 1783 with the Chevalier de Milletail (Carlo Brandt) visiting the elderly Monsieur de Blayac (Lucien Pascal), confined to his chair. He taunts him about his past prowess in wit and reminds him of how he humiliated him, naming him "Marquis de Clatterbang" when he fell over while dancing. He then urinates on the helpless old man.
Set in the period 1784–1789, the film portrays Jefferson when he was US minister to France at Versailles before the French Revolution. French liberals and intellectuals hope he will lead them away from the corruption of the court of King Louis XVI and Marie-Antoinette and toward a more democratic form of government. Although deploring the poverty of the common people, he embraces the riches of French culture and civilization. It is his first time abroad, and he takes advantage of the opportunity to extend his knowledge of liberal arts and science while absorbing the refinements France has to offer.
Napoleon Bonaparte (Charles Boyer) launches an unsuccessful seduction of the Countess Marie Walewska (Greta Garbo), who is married to a much older man (Henry Stephenson), but she resists until convinced that giving in will save Poland. After her husband annuls their marriage and Napoleon divorces the Empress Josephine, the pair are free to formalize their happy relationship, but Napoleon shocks her by announcing his decision to wed the Archduchess Marie Louise of Austria for political reasons. While he doesn't expect it to impact his relationship with Marie, she leaves him, without ever telling him that she is expecting his child.
Secret agent Nina Maria Azara (Jeanette MacDonald) is working undercover for the King of Spain (Tom Rutherford) as a singer known as the "Mosca del Fuego" or "Firefly." Despite her love for Captain Andre (Allan Jones), she tricks him so that his general will change the French defensive positions, thus allowing the Duke of Wellington to win the Battle of Vitoria. In the end Nina and Andre leave together for a new life in peace.
Jeanne de Saint-Rémy de Valois, orphaned at an early age, is determined to reclaim her royal title and the home taken from her family when she was a child. When she is rebuffed by Marie Antoinette and fails to achieve her goal through legal channels, she joins forces with the arrogant, well-connected gigolo Rétaux de Villette and her own wayward, womanizing husband Nicholas. They concoct a plan to earn her enough money to purchase the property.
On the eve of the French Revolution, Lucie Manette (Elizabeth Allan) is informed that her father (Henry B. Walthall) is not dead, but has been a prisoner in the Bastille for many long years before finally being released. She travels to Paris to take her father to her home in England. Dr. Manette has been taken care of by a friend, Ernest Defarge (Mitchell Lewis), and his wife (Blanche Yurka). The old man's mind has given way during his long ordeal, but Lucie's tender care begins to restore his sanity.
Just before the French Revolution, Henriette takes her close adopted sister Louise to Paris in the hope of finding a cure for her blindness. She promises Louise that she will not marry until Louise can look upon her husband to approve him. Lustful aristocrat de Praille (whose carriage kills a child, enraging peasant father, Forget-not) meets the two outside Paris. Taken by the virginal Henriette's beauty, he has her abducted and brought to his estate where a lavish party is being held, leaving Louise helpless in the big city. An honorable aristocrat, the Chevalier de Vaudrey helps Henriette to escape de Praille and his guests by successfully fighting a duel with him. The scoundrel Mother Frochard, seeing an opportunity to make money, tricks Louise into her underground house to be kept prisoner. Unable to find Louise with the help of the Chevalier, Henriette rents a room, but before leaving her de Vaudrey comforts and kisses the distressed woman. Later, Henriette gives shelter to admirable politician Danton, who after an attack by Royalist spies following a public speech falls for her. As a result, she runs foul of the radical revolutionary Robespierre, a friend of Danton.
André-Louis Moreau (Ramon Novarro) loves Aline de Kercadiou (Alice Terry), the niece of his godfather, Quintin de Kercadiou (Lloyd Ingraham), and she him. However Quintin would prefer she married the Marquis de la Tour d'Azyr (Lewis Stone), a middle-aged nobleman, rather than someone who does not even know who his parents are.
Already the most powerful man in France, Maximilien Robespierre (Richard Basehart) wants to become the nation's dictator. He summons François Barras (Richard Hart), the only man who can nominate him before the National Convention. Barras refuses to do so and goes into hiding.
The scenario of the film as originally written by Gance was published in 1927 by Librairie Plon. Much of the scenario describes scenes that were rejected during initial editing, and do not appear in any known version of the film. The following plot includes only those scenes that are known to have been included in some version of the film. Not every scene described below can be viewed today.
During a battle in the Aragonese town of Saragossa (Zaragoza) during the Napoleonic Wars, an officer retreats to the second floor of an inn. He finds a large book with drawings of two men hanging on a gallows and two women in a bed. An enemy officer tries to arrest him but ends up translating the book for him; the second officer recognizes its author as his own grandfather, who was a captain in the Walloon Guard.
On the last day of 1770, youngster Jonathan Blake (Freddie Bartholomew) overhears two sailors discussing something suspicious in his aunt's ale-house in a Norfolk fishing village. He persuades his more respectable best friend, Horatio Nelson (Douglas Scott), to sneak aboard the sailors' ship with him. They overhear a plot involving insurance fraud. When Jonathan decides to warn the insurers, Horatio cannot accompany him, because that same day he is invited to join the Royal Navy as a midshipman. Jonathan walks all the way to London to Lloyd's Coffee House, where the insurers conduct their business. Mr. Angerstein (Guy Standing), the head of one of the syndicates that make up Lloyd's of London, listens to him. Instead of a monetary reward, Jonathan asks to work at Lloyd's as a waiter. Angerstein teaches him that news, "honestly acquired and honestly shared," is the lifeblood of the insurance industry.