The newly transferred David Mills and the soon-to-retire William Somerset are homicide detectives who become deeply involved in the case of a sadistic serial killer whose meticulously planned murders correspond to the seven deadly sins: gluttony, greed, sloth, wrath, pride, lust and envy.
In a large unidentified city of near-constant rain, high levels of crime and urban decay, the two detectives are established in their wobbly partnership with starkly contrasting attitudes, personalities and lifestyles: in the opening scene, Somerset's diligent, controlled and alone as we follow his precise morning routine, opposing the relaxed Mills, who wakes up late next to his wife before dressing carelessly on his way to work. Somerset - the mature, cerebral cop - and Mills - headstrong, impulsive - are reluctantly partnered together, but they soon find common ground due to the gentle interference of David's wife Tracy. Weary, exhausted and pained Somerset is just one week away from a well-deserved retirement and fiery, idealistic hotshot Mills is touted as his cock-sure replacement; their next case will span the following seven days and change their lives forever. On Monday, the detectives discover an obese man who was forced to feed himself to death, representing "Gluttony." The next day, they discover a fatal bloodletting of a rich attorney, representing "Greed". The detectives find a set of fingerprints, as well as additional clues at both murder scenes, and believe they're chasing a serial killer relating to the seven deadly sins. Two days later, the fingerprints leads them to an apartment where they find an emaciated man strapped to a bed. Though he initially appears to be dead, it soon is discovered that the man has been kept alive and entirely immobile by the killer for exactly one year to the day; a drug dealer and child molester before his captivity, this victim represents "Sloth". Though unable to learn anything from the insensate victim, the detectives agree that the killer has planned these crimes for more than a year.
Tracy Mills is unhappy with their recent move to the city. She meets Somerset after the first two murders and he becomes Tracy's confidante. Upon learning that she is pregnant but has not told her husband, Somerset confides in her his fear that such an immoral, ravaged city is no place to start a family, and reveals that he had ended a relationship years earlier after pressuring his girlfriend to have an abortion. Somerset, knowing that David would more than likely want to keep the baby, advises her not to tell him if she plans to have an abortion.
Using library records, Somerset and Mills track down a man named John Doe, who has frequently checked out books related to the deadly sins. When Doe finds the detectives approaching his apartment, he opens fire on them and flees, chased by Mills. Eventually, Doe gains the upper hand and holds Mills at gunpoint, but then abruptly leaves, sparing Mills's life. Investigation of Doe's apartment finds handwritten volumes of his irrational judgments and clues leading to another potential victim, but no fingerprints. They arrive too late to find their "Lust" victim, a prostitute killed by an unwilling man wearing a bladed S&M device, forced by Doe to simultaneously rape and kill her, severely traumatizing the man. On Sunday morning, they investigate the death of a young model whose face had been mutilated. Having chosen to kill herself rather than live with a disfigured face, she is the victim of "Pride". As they return to the police station, Doe goes to the police station and offers himself for arrest, with the blood of the model and an unidentified victim on his hands. They find out that he has been cutting the skin off his fingers to avoid leaving fingerprints. Through his lawyer, Doe claims he will lead the two detectives to the last two bodies and confess to the crimes, or otherwise will plead insanity. Though Somerset is worried, Mills agrees to the demand. Doe directs the two detectives to a remote desert area far from the city; along the way, he claims that God told him to punish the wicked and reveal the world for the awful place that it is. He also makes cryptic comments toward Mills. After arriving at the location, a delivery van approaches; Somerset intercepts the driver, leaving Mills and Doe alone. The driver hands over a package he was instructed to deliver at precisely this time and location, which is 7 p.m. While Mills holds Doe at gunpoint, Doe mentions how much he admires him, but does not say why. Somerset opens the package and recoils in horror at the sight of the contents. He races back to warn Mills not to listen to Doe, but the killer reveals that the box contains Tracy's head. Doe claims to represent the sin of "Envy"; he was envious of Mills's normal life, and killed Tracy after failing to "play husband" with her. He then taunts the distraught Mills with the knowledge that Tracy was pregnant, asking Mills to kill him and become "Wrath". Somerset pleads with Mills not to let Doe win, but he cannot contain Mills, who then repeatedly shoots Doe, killing him, therefore completing his "work".
It is a nihilistic, bleak and somewhat depressive ending, but as such encapsulates and reiterates the entire thematic point of the film, that the world is a dark, hellish place that inhabits good and evil: those of whom commit horrendous crimes, and the people who try to stop them. In particular, Se7en is a serious artistic meditation on the ambiguous, murky nature of evil, depicted in the film as inhumanity, sin and crime; its city conjures up chillingly poetic imagery, presenting the destructive effects of crime with dirty, polluted and oppressively rain-soaked claustrophobia. Visually and stylistically, it is a grim, dark, dismal world, a look achieved through the chemical process of bleach bypassing, wherein the silver in the film stock was not removed, which in turn deepened the dark, shadowy images in the film and increased its overall tonal quality.
Complex, artistic and disturbing, Se7en is a brutal, grimy shocker that holds your mind captive to its psychologically violent subject matter and unforgettable imagery. It is not a masterpiece on the spectrum of more purely cinematic serial killer genre films such as The Silence of the Lambs, but it is interesting and thrilling enough to be called a work of jagged, uncompromisingly dark genius.