Kevin Lomax, portrayed by Keanu Reeves, is a highly successful defense attorney hailing from Gainesville, Florida, who has never lost a case. His confidence is tested when he represents a schoolteacher named Mr. Gettys (Chris Bauer), accused of child molestation. During the intense trial, Kevin comes to a disheartening realization about his client's guilt, compounded by a reporter's ominous warning that a guilty verdict is inevitable. Yet, through a fierce cross-examination, Kevin manages to tarnish the credibility of the victim (Heather Matarazzo), ultimately securing yet another not guilty verdict to celebrate.
In the aftermath of this triumphant moment, Kevin is approached by a representative from the prestigious New York law firm, Milton, Chadwick & Waters. The offer presented is enticing; he is promised a significant salary and the luxury of a lavish apartment in the city if he takes on jury selection duties. Despite his Evangelical Christian mother, Alice (Judith Ivey), expressing concerns about the sins lurking in the big city, Kevin eagerly accepts the job and relocates to Manhattan with his wife, Mary Ann (Charlize Theron).
As he begins his work at the firm, Kevin's first case involves defending a Voodoo sorcerer (Delroy Lindo) accused of performing a ritual animal sacrifice. In an effort to draw parallels with Kashrut law, he leverages the notion of religious freedom and ultimately wins the case. However, as his career flourishes, so does his obsession with work, causing him to neglect Mary Ann, who feels increasingly lonely and isolated.
Victorious yet consumed by his ambitions, Kevin's next challenge is defending Alexander Cullen (Craig T. Nelson), a billionaire implicated in the gruesome murder of his wife and child. This case further pulls Kevin into the depths of his profession, detracting from his relationship with Mary Ann. In the midst of this turmoil, Kevin begins to fantasize about his alluring co-worker, Christabella Andreoli (Connie Nielsen), while Mary Ann's mental well-being declines, as she insists on seeing demons surrounding her. Although Milton suggests to Kevin that he should withdraw from the trial, Kevin's stubbornness leads him to refuse.
The firm’s managing attorney, Eddie Barzoon (Jeffrey Jones), grows suspicious of Kevin, wrongly believing that he is vying for a higher position. His threats of exposing Kevin to the U.S. Attorney's office create tension, but Milton dismisses Barzoon's concerns, referring to him as "God's special little creature." A shocking turn of events occurs when Barzoon is brutally killed by vagrants, who appear to take on demonic forms, further fracturing Mary Ann's mental state.
As Kevin prepares for Cullen's case, he uncovers a web of lies from Cullen's mistress, Melissa (Laura Harrington). Despite recognizing Cullen’s guilt, Kevin chooses to follow through with the testimony, resulting in yet another acquittal. However, the victory is fleeting as Kevin finds Mary Ann in a vulnerable state at a nearby church, where she accuses Milton of a horrific assault. Conflicted and troubled, Kevin finds it hard to believe her claims and makes the devastating choice to have her committed.
Trouble escalates when U.S. Attorney Weaver confronts Kevin about the firm’s illicit activities, dropping a horrifying revelation that Gettys was discovered with a dead girl in his trunk. A tragic encounter leads to Weaver’s untimely demise in traffic, leaving Kevin in disarray. In a chilling twist, both Alice and Kevin's case manager, Pam (Debra Monk), visit Mary Ann, where Pam morphs into a demon before Mary's eyes. In a frenzied moment, Mary Ann attacks Pam, ultimately leading to her own tragic suicide by slashing her throat with a piece of glass.
Just as Kevin begins to process this devastating loss, Alice unveils a shocking truth: Milton is not just his boss; he is his father. Fueled by rage, Kevin confronts Milton, who revels in the fact that he manipulated events to bring about Mary Ann’s fate. Kevin, grappling with the realization that Milton is, in fact, Satan, becomes aware of his own role in this tragic narrative. Milton chillingly reveals his desire for Kevin and Christabella to conceive the Antichrist, offering Kevin anything he desires.
In a moment of defiance against his malevolent heritage, Kevin recognizes his free will and ends his own life, thwarting Milton's dark aspirations. The narrative twists back as Kevin awakens during a recess in the Gettys trial, facing Mary Ann once more. He makes a bold decision to withdraw from representing Gettys, disregarding the consequences that may follow. A reporter attempts to capture the moment, promising Kevin fame if he agrees to an interview. With a reluctant nod from Mary Ann, Kevin consents, leading to a shocking revelation as the reporter morphs into Milton, who ironically declares, > "Vanity - definitely my favorite sin."
