In 1780 in Frankfurt, Germany, youngster Nathan Rothschild warns his parents Mayer Amschel Rothschild and Guttle that the taxman is coming. They hurry and hide their wealth, including currency, silver, etc. The taxman demands 20,000 gulden, an exorbitant sum, but accepts a bribe of 5000 in exchange for assessing 2000 in taxes. Mayer's satisfaction is short-lived, however; a courier bringing him 10,000 gulden is intercepted and the money confiscated by the taxmen. Mayer tells his sons that he tries to be as honest as possible, but the antisemitic authorities will not let him; he admonishes his children to acquire money, for "money is power" and a defense for their people. Later, as Mayer Rothschild is lying on his deathbed, he instructs his five sons to start banks in different countries across Europe: Amschel in Frankfurt, Salomon Mayer von Rothschild in Vienna, Nathan in London, Carl in Rome, and James in Paris. That way, they can avoid having to send gold back and forth as the need arises, for in war they are in danger of being robbed by the enemy and in peace by their own countrymen. Instead, they can draw on each other's banks. Thirty-two years later, the sons have established banking houses. Then France overruns Europe in the Napoleonic Wars. Austrian Prince Metternich asks Salomon to raise 15 million florins to help defeat Napoleon. The other brothers are approached with similar requests. Even in France itself, Talleyrand asks for 50 million francs. Nathan refuses to loan the British Government five million pounds to hold off the enemy, but offers the Duke of Wellington twice that amount to smash him. After the war is won, Wellington is disappointed to find that Nathan Rothschild has not even been invited to a party in the duke's honour. He insists on going to see Nathan. His aide, Captain Fitzroy, knows the address, as he is in love with Nathan's daughter, Julie, and vice versa. While there, Wellington tells Nathan that the victorious powers are going to make a very large loan to France to help it recover from the war. The winning underwriter will become the most powerful and prestigious bank in Europe. Nathan's bid is the best, but is rejected in favor primarily of Barings Bank. When Nathan demands to know the reason, Prussian Count Ledrantz explains it was discarded on a "technicality", because Nathan is a Jew. Nathan surmises that the quarter of the loan not awarded to Barings will fall to Ledrantz, Metternich and Talleyrand, who stand to make enormous profits. Nathan outmanoeuvres them financially, bringing them to the brink of ruin and dishonour; they capitulate and surrender to him the entire loan. However, this has somewhat embittered him. Where once he accepted Julie's choice, he now tells the non-Jewish Fitzroy to stay away from her. Anti-Jewish riots break out all over Germany, instigated by Ledrantz. Nathan returns to Frankfurt and, under pressure from his own people, agrees to submit to Ledrantz. However, before he can, he receives word that Napoleon has escaped from exile. Nathan's brothers, fearful of their positions, want to support the restored French dictator. However, Nathan refuses to do so. With Ledrantz and others once again desperately in need of financial support, he extracts a treaty from them granting Jews rights, freedoms and dignity long denied them. He also tells Fitzroy that he can once again see Julie. With Napoleon seemingly invincible, Nathan determines to risk all in support of the allies. Just before he is bankrupted, he receives word that Wellington has won the Battle of Waterloo, and he is not only saved, he becomes the richest man in the world and a baron.
The film was the biggest hit of the year for Twentieth Century Pictures. The film was one of United Artists most popular films of the year. It was nominated for the Academy Award for Best Picture. A scene from The House of Rothschild was used in the German antisemitic propaganda film The Eternal Jew without the permission of the copyright holders.
