Being the adventures of a young man whose principal interests are rape, ultra-violence and Beethoven.
Sometime in the not-to-distant future, gangs of teenage thugs roam rubble-strewn streets, terrorizing citizens who sequester themselves behind locked doors. Alex, the leader of one of the gangs, and his "droogs," Pete, Georgie and Dim, distinguish themselves by wearing all-white, cod pieces, bowler hats and walking canes as the spend their nights committing rapes, muggings and beatings for entertainment. One night, after stopping at the Korova Milk Bar for the house specialty, drug-laced milk that induces "ultra violence," the group kicks an elderly tramp mercilessly. Finding rival gang leader Billyboy and his hoodlums raping a woman nearby, Alex and his droogs take a moment to enjoy the scene then use chairs, broken bottles and knives to pummel the other gang unconscious. The gang speeds off in their Durango 95 sports car playing a game called "hogs of the road," which entails forcing other drivers off the road. Spotting a wealthy residence displaying the sign "HOME," the gang gains admittance by claiming that they need to use the phone to report an accident.
Once inside, Alex beats and kicks the home's owner, writer Mr. Frank Alexander, while mimicking a soft shoe dance routine and singing a musical number. After the droogs shove balls into the mouths of Alexander and his wife and wrap their heads in tape, Alex rapes Mrs. Alexander as Mr. Alexander watches helplessly. Later, Alex returns to municipal flatblock 18A, a disheveled modern apartment building where he lives with his cowardly mum and dad. After stashing stolen money and watches, Alex listens to his favorite composer, Beethoven, plays with his pet snake and dreams of further violence. The next morning, Alex refuses to go to school, claiming that his work, "helping here and there," has left him exhausted. Soon after, a government probation officer, Mr. Deltoid, arrives at the flat and knees Alex in the genitals for reverting to outbursts of violence and wasting the government's resources trying to reform him. Unaffected by the visit, Alex picks up two young women at a record shop and brings them back to his room to have sex, becoming so involved that he misses a gang meeting.
Later, after his droogs express their disappointment to Alex about his missing their meeting and Georgie rebukes him for picking on Dim and then suggests they commit larger robberies. Outraged at the insubordination, Alex knocks Georgie into a river and knifes Dim's arm when he tries to help Georgie. Having reasserted his authority, Alex appropriates Georgie's suggestion. The gang then proceeds to the home of health club owner Mrs. Webber, who is known as "Catlady" and lives alone with her dozens of cats. Having read about the Alexanders, Webber refuses the gang entrance when they attempt the accident ruse again, but Alex then breaks into the house and bludgeons Webber unconscious with a large sculpted phallus, part of Webber's erotic art collection. Hearing approaching sirens, Alex flees outside, where his droogs, fed up with Alex's brutality, bash him unconscious and leave him for the police. After Webber dies from her injuries, Alex is sentenced to 14 years in prison. During his jail admittance procedure, Alex must submit to an autocratic officer who assigns him a number to replace his name, strips him of clothes and belongings and performs an anal search.
For his first two years, Alex panders to the prison chaplain by quoting the Bible and accompanying him on keyboard for service hymns, while secretly fantasizing about the Bible's violent and sexual passages. One day, Alex, hoping for an early release from jail, claims that he wants to reform permanently and asks the chaplain to help him get on the list for an experimental treatment of aversion therapy known as the Ludivicko technique, but the chaplain warns him that the brainwashing program will erase his will and therefore his soul. Soon after, the unscrupulous Minister of the Interior, hoping the aversion therapy will win his government valuable public support, chooses the enthusiastic Alex as the first candidate and sends him to the Ludivicko Center, where Alex is promised that he will be permanently cured in two weeks. Alex is then injected with a serum that causes him to feel waves of excruciating nausea and suffocation, which he names the "sickness," when his violent passions arise. Bound in a straightjacket with his eyelids forced open by clamps, Alex is forced to watch hours of violence and mass destruction as part of his conditioning to repulse violence.
On the second day of treatment, when the attending doctors play Beethoven's ninth symphony during the screenings, Alex realizes that the music of his favorite composer will now forever be associated with "the sickness," and begs them to stop, but the doctors refuse. The day before his release, Alex is presented on a stage before an audience of government officials and other authorities to prove the treatment's validity. Alex's fear of "the sickness" prompts him to follow orders and submit to degrading treatment without reacting with violence. When he is then presented with a nude woman, Alex at first grasps for her, but the sickness prevents him from even touching her. Although the chaplain loudly protests that Alex has lost all choice and deems the treatment unethical, the Minister of the Interior proclaims it a success and releases Alex.
Returning home, Alex discovers that his parents have taken a lodger, Joe, who defends his mum and dad and protests that Alex should not be allowed to return because of his atrocious behavior. Learning that the police have taken away his belongings and his snake is dead, Alex leaves the apartment sobbing and contemplates suicide at the river. When a tramp interrupts to ask for change, the man recognizes Alex as the brutal youth who beat him years ago, and leads him to a tunnel teaming with elderly drunkards who accost him. Police officers stop the fight, but Alex soon recognizes the officers as Georgie and Dim, who are happy to mete out their revenge against their former leader. They handcuff Alex and drive him to an isolated area where they nearly drown him in an animal trough while laughing at the cruel spectacle. Weak, soaking and unable to recognize his surroundings, Alex mistakenly seeks help at "HOME." Alexander, who lost his wife to suicide just after Alex and the dross's attack, recognizes Alex only as the man in the newspaper who was forced to submit to the police's inhumane experiments and offers him a bath and dinner.
However, when Alex starts humming his signature show tune, Alexander then realizes that Alex is his previous assailant and concocts a plan. Thinking Alex's behavior modification treatment unjust, the politically subversive writer calls several journalists who arrive shortly after to use Alex's testimony for their own political agenda. After learning that his conditioning includes a severe aversion to Beethoven, the writer serves Alex sedative-laced wine, locks him a room and tortures Alex by playing Beethoven at a deafeningly loud volume. Alex attempts suicide by jumping from the second story window, but the fall succeeds only in broken bones that result in an extended stay at a hospital. Newspapers soon report Alex's attempt as proof of the government's inhumanity, thus prompting the government to hire psychiatrist Dr. Taylor to reverse the Ludivicko conditioning. The doctor then tests Alex by presenting him with cartoons with open-ended narratives. Alex happily creates violent dialogue for his characters, thus proving his "recovery."
Soon after, the Minister of Interior visits Alex with an offer. Reminding him that the writer and several of his other victims would like him either killed or imprisoned, the minister, worried about the outcome of the election, offers Alex a job and financial compensation in trade for being the minister's propaganda tool. As Alex accepts the proposal, the press photographs the two men to publicize the government's change of heart. When Beethoven's ninth symphony is then played, Alex spontaneously imagines scenes of public fornication and happily announces that he is "cured indeed."
- 2HR 15MIN ' R