In 1987, Patrick Bateman is a young Harvard Business School graduate from a wealthy family who works at an investment banking firm on Wall Street named Pierce & Pierce. Patrick attends a dinner party at his girlfriend Evelyn's apartment, along with his colleague Tim Price, his secret mistress Courtney, and a bohemian couple named Vanden and Stash. Patrick spends his free time perfecting his beauty regimen, buying luxury products, exercising, watching daytime talk shows, and squabbling with colleagues over men's fashion etiquette. At a restaurant named Pastels, Patrick is humiliated when the quality of his business card pales in comparison to his co-workers'. Later in the night at a club named Tunnel, Patrick and Tim snort cocaine in the bathroom, before Tim vanishes. The next day, Patrick runs into Tom Cruise in the elevator of his building.
Patrick is resentful when a date named Patricia is disappointed that he cannot reserve a table at an exclusive restaurant named Dorsia. At a dry cleaner, Patrick berates an employee for failing to remove blood from his laundry, which he passes off as juice stains. Later, sitting with a group at a bar named Harry's, Patrick is unsettled when his colleague Paul Owen introduces a friend named Paul Denton, who seems to recognize Patrick. Patrick also realizes that Paul Owen thinks he is a different Pierce & Pierce executive named Marcus Halberstam. One day at work, Patrick and another colleague named Luis Carruthers—who is dating Courtney—are dazzled by Paul Owen's fashionable tie and hairstyle. Patrick takes Evelyn to dinner after her neighbor is found decapitated. After leaving a black-tie event early, Patrick violently stabs a homeless man and his dog to death on the street, then goes to McDonald's and orders a milkshake.
At a U2 concert, Patrick feels a fleeting yet transcendent connection to the lead singer, Bono. Later, having lunch at the Yale Club, Patrick wonders if Courtney would like him better if Luis were dead. However, when Patrick follows Luis into the bathroom to try to strangle him, Luis mistakes his touch for a sexual overture, repulsing Patrick. Patrick later murders an older gay man and his sharpei on the Upper West Side. Ditching Courtney one night after dinner, Patrick takes a blonde sex worker back to his apartment in his limousine, and calls another via an escort service. Patrick and the girls, whom he calls Christie and Sabrina, have sex that leaves them bloodied. Before Evelyn's Christmas party, Patrick kills a Chinese delivery boy on the street, and later forces Evelyn to leave the party with him, after she almost alerts Paul Owen to the fact that Patrick is not in fact Marcus Halberstam. Another night, Patrick takes a model named Daisy home but tells her to leave before he can succumb to his violent urges.
After meeting Paul Owen for dinner one night, Patrick lures him back to his apartment, where he murders Paul with an axe, then uses his keys to break into his apartment. While shopping one day, Patrick panics when he runs into Luis, who confesses his desire for Patrick. Later, Patrick is annoyed when his younger brother Sean is able to secure a table at Dorsia. Patrick goes on a lunch date with an old college acquaintance named Bethany, whom he takes home and brutally rapes and murders. At work one day, Patrick offers to take his secretary Jean anywhere for dinner. When she chooses Dorsia, Patrick pretends to have a reservation, but the two are ejected from the restaurant, and Patrick declines Jean's advances at the end of the night. Sometime in August, a detective named Donald Kimball hired to investigate Paul Owen's disappearance visits Patrick at Pierce & Pierce, but can find no leads.
Toward the summer's end, Patrick and Evelyn stay at Tim Price's vacation house in the Hamptons, but return to the city after becoming bored and restless. Patrick leaves his dinner group one night to pick up Christie again, whom he takes back to his apartment along with his date named Elizabeth. While they are having sex, Patrick tortures and murders them both. Patrick once again runs into Luis while shopping, who tearfully tells Patrick he is transferring to Arizona. While walking through the Central Park Zoo, Patrick murders a child in the penguin habitat. Another night, Patrick uses Paul Owen's apartment for a date with two escorts named Torri and Tiffany, whom he also rapes and murders. While trying to organize dinner plans one night, Patrick accidentally tells Evelyn and another date named Jeannette to meet him at the same restaurant, where he never shows. After finding a rat emerge from his toilet, Patrick uses it to defile the body of a nameless woman while murdering her.
Patrick breaks up with Evelyn, and later cries while cannibalizing the remains of his victims in his apartment. Patrick wanders out of a group dinner one night and murders a saxophonist and a taxi driver, alerting nearby police, who chase Patrick into his office building. In his office, Patrick calls a man named Harold Carnes and leaves a voicemail confessing to all of his crimes. Later, Patrick visits his mother at a private facility called Sandstone. When Patrick tries stopping by Paul Owen's apartment, an imperious real estate agent tells him to leave. Patrick continues to resist Jean's advances, and forces Jeannette to undergo an abortion procedure. One day at work, Tim suddenly reappears, perplexing Patrick. Another night at a club, Patrick runs into Harold Carnes, who calls him "Davis" and dismisses his voicemail confession as a practical joke. After breakfast one day, Patrick is held up by a taxi driver, who accuses Patrick of killing his friend and steals his Rolex. Later, having drinks with colleagues, Patrick watches with disinterest as Ronald Reagan speaks at George H. W. Bush's inauguration.