It's sometime in the 21st century and survivors of the third world war have realized that the volatile nature of humans can no longer be risked. Accordingly, the ruler of the land, Father (SEAN PERTWEE), has decreed through his powerful right-hand man, Dupont (ANGUS MACFADYEN), that all human emotions be suppressed.
Accordingly, everyone is ordered to take their daily dose of emotion-eliminating Prozium, while all artwork has been deemed dangerous and thus earmarked to be destroyed upon discovery. To make sure this occurs, a highly trained and lethal group of law enforcers known as the Gramaton Clerics has been called into action and none are as proficient as John Preston (CHRISTIAN BALE). Not only did he not intervene when his wife (MARIA PIA CALZONE) was executed for breaking the law, but he's also just killed his partner, Partridge (SEAN BEAN), for hording a forbidden literary work.
Now raising his two kids, Robbie (MATTHEW HARBOUR) and Lisa (EMILY SIEWERT), by himself, Preston finds himself partnered with the overzealous Brandt (TAYE DIGGS) who's determined to help Father and Dupont find and wipe out a rebel underground movement led by Jurgen (WILLIAM FICHTNER).
Yet, when Preston inadvertently doesn't take his Prozium for a day, he's soon overwhelmed by emotions as well as the words of captured dissident Mary O'Brien (EMILY WATSON) who causes him to question his place and purpose in a world where emotion is outlawed. From that point on, Preston suddenly finds himself labeled by his own as the enemy and does what he can to find Jurgen and his followers while avoiding Brandt and others who want to capture and kill him.