On the Western Front in 1918, a Jewish Private fighting for the Central Powers nation of Tomainia valiantly saves the life of a wounded pilot, Commander Schultz, who carries valuable documents that could secure a Tomainian victory. However, their plane crashes mid-flight, and the Private subsequently suffers memory loss. Upon being rescued, Schultz is informed that Tomainia has officially surrendered to the Allied Forces, while the Private is carried off to a hospital.
Twenty years later, still suffering from amnesia, the Private leaves the hospital to return to his previous profession as a barber in the ghetto. The ghetto is now governed by Schultz, who has been promoted in the Tomainian regime under the ruthless dictator Adenoid Hynkel.
The Barber falls in love with a neighbor, Hannah, and together they try to resist persecution by military forces. The troops capture the Barber and are about to hang him, but Schultz recognizes him and restrains them.
Meanwhile, Hynkel tries to finance his ever-growing military forces by borrowing money from a Jewish banker called Hermann Epstein, but the banker refuses to lend him the money. Furious, Hynkel orders a purge of the Jews. Schultz protests this inhumane policy and is sent to a concentration camp. He escapes and hides in the ghetto with the Barber. Schultz tries to persuade the Jewish family to mount an assassination attempt against Hynkel, but they decline to participate. Troops search the ghetto, arrest Schultz and the Barber, and send both to a concentration camp. Hannah and her family flee to freedom in the neighboring country of Osterlich. Hynkel has a dispute with the dictator of the nation of Bacteria, a man named Napaloni, over which country should invade Osterlich. After signing a treaty with Napaloni, Hynkel invades Osterlich, with Hannah and her family being trapped by the invading force.
Escaping from the camp in stolen uniforms, Schultz and the Barber, dressed as Hynkel, arrive at the Osterlich frontier, where a huge victory-parade is waiting to be addressed by Hynkel. The real Hynkel is mistaken for the Barber while out duck hunting in civilian clothes and is knocked out and taken to the camp. Schultz tells the Barber to go to the platform and impersonate Hynkel, as the only way to save their lives once they reach Osterlich’s capital. The Barber has never given a public speech in his life, but he has no other choice.
The terrified Barber mounts the steps but is inspired to seize the initiative. Announcing that he (as Hynkel) has had a change of heart, he makes an impassioned plea for brotherhood and goodwill.
You, the people, have the power to make this life free and beautiful, to make this life a wonderful adventure.
Then – in the name of democracy – let us use that power – let us all unite. Let us fight for a new world – a decent world that will give men a chance to work – that will give youth a future and old age a security. By the promise of these things, brutes have risen to power. But they lie! They do not fulfill that promise. They never will!
Dictators free themselves but they enslave the people! Now let us fight to fulfill that promise! Let us fight to free the world – to do away with national barriers – to do away with greed, with hate and intolerance. Let us fight for a world of reason, a world where science and progress will lead to all men’s happiness. Soldiers! in the name of democracy, let us all unite!
Finally, he addresses a message of hope to Hannah, in case she can hear him.
Look up, Hannah. The soul of man has been given wings, and at last he is beginning to fly. He is flying into the rainbow – into the light of hope, into the future, the glorious future that belongs to you, to me, and to all of us.
Hannah hears the Barber’s voice on the radio. She turns her face, radiant with joy and hope, toward the sunlight, and says to her fellows, “Listen.”