In 1987, the affluent New York investment banker Patrick Bateman leads a life defined by extravagant dinners at fashionable restaurants and maintaining his polished facade for his fiancée Evelyn and his circle of wealthy yet superficial acquaintances, whom he largely detests. Bateman details the ostentatious aspects of his lifestyle, including his rigid daily regimen of exercise and grooming. He passionately describes his eclectic music collection, featuring artists like Huey Lewis and the News, Phil Collins, and Whitney Houston. His obsession with wealth is further highlighted by his taste for high-end designer wear and his opulent apartment.
While Bateman engages in an affair with Evelyn's friend Courtney (portrayed by Samantha Mathis), Evelyn herself is reciprocating with Bateman's colleague Timothy (played by Justin Theroux). This tangled web of infidelity extends to Courtney, who is betrothed to Bateman's other coworker Luis Carruthers (who exhibits mildly homosexual tendencies). Bateman and his cohorts revel in their vanity as they flaunt their business cards. This vanity reaches a deadly peak when Bateman, fueled by jealousy over coworker Paul Allen's (depicted by Jared Leto) superior business card, commits the heinous act of murdering a homeless individual along with the man's dog.
At a Christmas gathering, the stage is set for a grim plot as Bateman arranges to dine with Paul, who mistakes him for another coworker, Marcus Halberstram (Anthony Lemke). Once Paul is intoxicated, Bateman lures him back to his apartment, where he shares an interpretation of "Hip to Be Square" before brutally murdering him with an ax, wearing a raincoat to shield himself from the splatter of blood. After disposing of Paul's body, Bateman visits Paul's apartment to fabricate a story that he has relocated to London.
Later, Bateman is confronted by private detective Donald Kimball (Willem Dafoe) in his office regarding Paul’s disappearance. That evening, he invites two prostitutes—Christie (Cara Seymour) and Sabrina (Krista Sutton)—to his apartment, where he discusses how the band Genesis evolved from progressive rock to pop with their album Duke. Subsequently, he violently assaults the prostitutes, ensuring that he introduces himself as Paul Allen.
The next day, Bateman encounters Luis Carruthers, who reveals his new business card, which triggers a violent reaction from Bateman. However, in a twist of fate, Luis misinterprets Bateman's aggressive demeanor as a proposal of love, leaving Bateman disgusted and fleeing. Following the murder of a model, he invites his secretary Jean (Chloë Sevigny) to his apartment under the pretense of drinks, where he holds a nail gun to her head but dismisses her when receiving a call from Evelyn.
Bateman has a violent threesome with his friend Elizabeth (Guinevere Turner) and Christie at Paul's now-vacant apartment. The encounter turns deadly when he kills Elizabeth mid-act, leading the terrified Christie to run for her life, only to be met with Bateman's wrath as he drops a chainsaw on her from above.
The relationship with Evelyn crumbles as Bateman stumbles upon a stray kitten while using an ATM, which commands him to "feed me a stray cat." He contemplates shooting the cat, but after a woman intervenes, he shoots her instead and lets the cat flee. Bateman sparks a police chase, obliterating police cars in a fit of rage. In an act of desperation, he enters a wrong office building, resulting in the murder of a security guard and a janitor. Bateman frantically leaves a confession on his lawyer Harold’s (Stephen Bogaert) answering machine.
The following day unveils Bateman’s paranoia when he discovers Paul's apartment is vacant, completely devoid of any sign of his atrocities. As Bateman prepares for a meeting with his colleagues, Jean uncovers explicit drawings of murder and torture in his journal. During a chance meeting at a restaurant, Bateman attempts to confess his crimes to Harold, who dismisses the phone message as a joke, convinced that he had dined with Paul days earlier.
Ultimately, Bateman confronts a chilling reality. In a haunting voice-over, he recognizes that his department of sins has no reckoning, and that his whispered confessions amount to nothing more than an illusion of guilt: "This confession has meant nothing."
