Equilibrium is set in a dystopian city-state of Libria. After a Third World War devastated the Earth, a totalitarian state emerged whose ideology determined human emotion to be the root cause of conflict. All emotionally stimulating material is banned and "sense offenders" are ruthlessly persecuted. Illegal materials are rated "EC-10" for "emotional content" and incinerated. Everyone is required to take daily injections of Prozium, an emotion-suppressing drug.Libria is governed by the Tetragrammaton Council, which is led by a reclusive figurehead known as "Father" (Sean Pertwee). Father never interacts with anyone directly, but he is seen on giant video screens throughout the city. The Tetragrammaton Council uses the police to enforce conformity. At the pinnacle of Librian law enforcement are the Grammaton Clerics, who are trained in the martial art of gun kata. The Clerics raid the "Nether" region outside the city, where they destroy emotionally stimulating materials such as art, books and music, executing the people hiding them. Despite their efforts, a resistance movement, known as the "Underground", has emerged. John Preston (Christian Bale) is a high ranking Grammaton Cleric and a widower with two children whose wife, Viviana (Alexa Summer), was executed for "Sense Offense". After a raid, Preston notices his partner, Errol Partridge (Sean Bean), taking a book of poems instead of incinerating them. Realizing Partridge is keeping the book, Preston tracks him down and executes him. Before he dies, Partridge says that all the consequences of feeling are a cost he "would pay gladly". The next morning, Preston accidentally breaks his daily vial of Prozium, and as he does not have an immediate replacement, he begins to experience emotions. Upon gaining replacement vials, he decides against taking them and instead hides them behind the mirror in his bathroom.Preston is partnered with career-conscious Brandt (Taye Diggs). Together, they arrest Mary O'Brien (Emily Watson), for sense offense. Preston's emotional confusion is exacerbated during her interrogation. Without Prozium, Preston finds it difficult keeping an emotionless facade in front of his son (Matthew Harbour) and his suspicious partner. Preston forges an emotional connection with O'Brien and he feels remorse for killing Partridge, especially after he finds out that Partridge and O'Brien were lovers. He eventually contacts the Resistance and is then summoned before Vice-Counsel DuPont (Angus Macfadyen) who reveals there is a traitor in the clerics. DuPont tells him to exterminate the Resistance and to find the traitor. The Resistance convinces him to assassinate Father to start a revolution. They plan to disrupt Prozium production which will then lead to an uprising by the populace.After Preston fails to stop Mary O'Brien's execution, he is caught having an emotional breakdown by Brandt, who arrests him and brings him before the Vice-Counsel. After tricking DuPont into believing that Brandt is the real traitor, Preston is informed that a search of his home will take place as a formality. He rushes home to destroy the hidden vials of unused Prozium before the search team can find them, only to find the search team is already inside and searching. He proceeds directly to where he had hidden the vials, but finds that his son — who reveals that he stopped taking Prozium after his mother died — has already taken the unused vials from their hiding place to prevent the search team from finding them.As planned, the leaders of the Resistance are captured and Preston is granted an exclusive audience with Father. Father actually turns out to be DuPont, who replaced the original Father after his death. Preston goes on a rampage, fighting his way to DuPont's office, which is filled with artwork and ornate furniture, all illegal items. It is revealed that Brandt was not arrested, but was part of a ruse to expose Preston. It also becomes clear that DuPont does not take Prozium and has been reading poetry. DuPont taunts him, asking Preston how it felt to betray the Underground. Preston kills all of DuPont's bodyguards, and defeats Brandt in a katana battle. Preston and DuPont finally fight in a gun kata battle, which Preston wins.DuPont tries to convince Preston to spare him, asking if taking his life is worth the emotion of knowing he killed someone who is "feeling" and knows how beautiful life can be. Preston repeats Partridge's last words and announces that he gladly will pay the cost, shooting DuPont in the chest. He then destroys the propaganda communication control systems, freezing all of the indoctrination propaganda everyone had been subjected to all their lives. The Underground blows up the Prozium manufacturing and storage facilities, while scores of rebels successfully attack key points throughout the city. Preston quietly watches the overthrow of the government from DuPont's office, holding O'Brien's red ribbon and smiling.