John Preston is the protagonist of the film. He holds the rank of Grammaton Cleric First Class, a man trained to locate and arrest those guilty of feeling. His intuitive ability to discern sense-offenders, people who have halted their doses of Prozium and can feel emotion, gives him the aptitude to hunt these people down. Furthermore his perfection of Gun Kata, which is a fictional gun-fighting martial art discipline, and his lack of emotions make him the deadliest of enforcers.
After a raid in the Nethers, the ruins of cities destroyed in World War III where the sense-offenders live and hide-out, Preston senses something in his colleague Partridge, a Grammaton Cleric First Class. He finds him reading a book in a ruined Cathedral in the Nethers, where he speaks of emotion and forces Preston to kill him. Afterwards Preston accidentally breaks the vial of his morning dose of Prozium and begins to experience emotions. The death of his partner shakes him and he deliberately goes off the medication.
During the next raids Preston tries to save some resistance fighters and saves a puppy. The consequence of his feelings is that he kills several officers in order to reveal that he is a sense-offender. Through an interrogation with a woman named Mary, who turns out to be Partridge’s lover, Preston comes into contact with the resistance. Additionally he agrees to