In a dystopian England, a sociopathic delinquent named Alex and his gang of "droogs" partake in a series of violent and sadistic crimes, including assault, robbery, and rape. Alex's love for classic music, particularly Ludwig van Beethoven, contrasts sharply with his thrill-seeking antisocial behaviors. The gang operates under a totalitarian regime, reveling in brutality and indulging in "a bit of the old ultra-violence." Alex is portrayed as both a charming yet deeply flawed character, whose interests in high culture do nothing to quell his violent impulses.

When a heist goes wrong, resulting in the death of a woman, Alex is betrayed by his droogs and arrested by the police. Facing a long prison sentence, he becomes aware of an experimental behavior correction program. This offers him the opportunity for an early release, which he eagerly accepts without fully understanding the consequences. The experimental treatment is a controversial technique aimed at rehabilitating criminals by conditioning them to associate feelings of sickness with violence, thus stripping them of their ability to commit crime.