In a futuristic, state-run society controlled by "Big Brother" in which love is outlawed, employee of the state Winston Smith falls for Julia, and is tortured and brainwashed for his crime.
In a totalitarian future society, Winston Smith, whose daily work is re-writing history, tries to rebel by falling in love.
- A voice-over narrator explains that in 1955, a nuclear war and devastation of Earth gave rise to three powerful police superstates continually at war with one another: Oceania, ruled by the omnipresent Big Brother; Eurasia ruled by the communists, and finally East Asia ruled by a sub-branch of socialists. By 1984, London, with its bomb-proof ministry, was designated as the capital of Airstrip One, a province of Oceania.
In the spring of 1984, as the sound of air raid sirens wail above the London streets, Winston Smith (Edmond O'Brien), a member of the elite Outer Party, takes cover in a doorway and there encounters Julia (Jan Sterling), a woman he suspects may be a member of the Thought Police. After the air raid sirens abate, Winston goes to his apartment, where an electronic surveillance eye examines the contents of his briefcase. Smuggling a small black diary past the eye, Winston begins to write down the subversive thoughts he fears to say aloud. Winston's reverie is interrupted when Selina Parsons (Carol Wolveridge), the little girl who lives next door and is training to become a spy for Big Brother, enters his apartment to practice denouncing him as a traitor. After his daughter heads off for her spy indoctrination, Parsons (Donald Pleasence), Selina's father, invites Winston to join him at the local Chestnut Tree café for some tea.
At the cafe, Winston and Parsons spot Rutherford and Jones, two traitors who have been rehabilitated by the government's Ministry of Love. After Big Brother impulsively orders Rutherford and Jones's re-arrest, Winston, rattled, goes to a junk shop to wonder at the beauteous objects of yesteryear that are now deemed worthless. As the elderly proprietor (David Kossoff) shows Winston his wares, Julia enters the shop, sending Winston scurrying into the street, where he is stopped by the police and ordered to report to Administration the next morning.
At the Administration the next day, a party officer reprimands Winston for mixing with the common masses (the Proles). Winston then proceeds to his job at the Records Department, where he revises history to vindicate Big Brother's pronouncements. When Winston discovers a photo that would prove Jones and Rutherford innocent, O'Connor (Michael Redgrave), Winston's superior and a minister of the exclusive Inner Party, instructs him to destroy it.
That evening, at a political rally to foment hate against Eurasia, Julia passes Winston a note professing her love to him. Later, they arrange to meet Sunday in a meadow, far from the prying microphones and monitors of Big Brother. There, they touch each other, an act prohibited by the Anti-Sex League and proceed to make love (off-camera).
Two weeks later, Winston and Julia meet clandestinely at a bell tower, and Winston proposes renting a room at the junk store, one of the few places free of the omnipresent monitors. The elderly proprietor honors their request and sets up a cozy bedroom and kitchen for them. In the sanctity of their quarters, after Julia removes her austere party uniform and dons a frilly blouse, Winston confides that he believes O'Connor may be a member of the Underground.
One night, while leafing through his diary, Winston finds a note written in O'Connor's hand that reads "down with Big Brother." The next day at work, O'Connor tells Winston to come by his apartment that evening to pick up some documents. Convinced that O'Connor represents their only hope to break free of the tyranny of Big Brother, Julia and Winston go to his apartment and declare that they want to join the Underground. After drinking a toast to the demise of Big Brother, O'Connor asks if there is anything they would not do for the Underground and Julia replies that she would not be separated from Winston. O'Connor then instructs Winston to carry an empty briefcase with him at all times.
During a rally to launch Hate Week, a man in the crowd switches briefcases with Winston, and when Winston opens the case, he finds a copy of a treatise by Calidor, the alleged leader of the Underground. Back in their secret room, Julia muses that only love can defeat Big Brother and thus provide hope for the future. At that moment, a telescreen hidden behind a mirror breaks its silence to condemn Julia's sentiments, after which, the police, accompanied by the elderly proprietor, burst in to arrest them.
At the Ministry of Love, Winston is confined in a pit-like room for hours (and probably days). Soon after, Parsons is thrown into the pit, his daughter having denounced him for muttering in his sleep "Down with Big Brother." Under O'Connor's direction, Winston is subjected to a brainwashing campaign. Still resistant after a series of electroshock treatments, Winston declares that the party will never eradicate his love for Julia. O'Connor then ushers Winston into the dreaded Room 101, where each prisoner must confront their own personal terror. Having ascertained that Winston's worst fear is being eaten alive by rats, O'Connor confines him in a room filled with the squealing rodents, after which he breaks down and begs them to feed Julia to the rodents instead. His will broken, the door opens and Winston falls sobbing into O'Connor's arms.
After O'Connor authorizes his release, Winston mindlessly wanders through the streets, where he spots Julia, her eyes vacant as his, seated on a bench. After they confess their mutual betrayal, Big Brother broadcasts that the Eurasian army has been routed. In the final shot, the rehabilitated and brainwashed Winston and Julia then fervently join the crowd cheering "Long live Big Brother!"