Tess McGill, portrayed by Melanie Griffith, is a determined 30-year-old secretary working at Petty Marsh, a sprawling financial firm in Manhattan. With aspirations to climb the corporate ladder and break free from her secretarial role, Tess eagerly seeks an executive position. However, her path is obstructed; her business degree from a non-elite school disqualifies her from the company’s training program for fresh graduates. To combat this, she enrolls in speech classes in an effort to refine her vocal delivery, sharing her ambitions with her close friend and fellow co-worker, Cynthia, played by Joan Cusack, during their daily ferries across the city.
In her pursuit of career advancement, Tess's supervisor, David Lutz (Oliver Platt), takes notice of her aspirations and gives her the contact details for his colleague, Bob Speck (Kevin Spacey). Unfortunately, Tess's excitement turns to disgust when she meets Speck, a lewd and drug-abusing man who makes unwanted advances towards her in his limousine, prompting her to escape in indignation. Fueled by anger, she humiliates Lutz by sending a scathing message via the office stock ticker.
Just when Tess thinks things might improve, she is transferred to a new division and becomes the secretary for Katharine Parker, a dynamic mergers executive brilliantly played by Sigourney Weaver. Initially apprehensive, Tess is pleased to start working for a woman and is taken aback to discover that Katharine is younger than her. Katharine welcomes Tess with open arms, promising support and an open line of communication.
Tess enthusiastically shares her new job with her indifferent boyfriend, Mick (Alec Baldwin), who shows little interest in her professional aspirations. Undeterred, Tess immerses herself in observing Katharine’s impressive command of the business world, admiring her confidence amidst the male-dominated environment. When Petty Marsh lands a contract with Trask Industries, Tess proposes an innovative radio investment strategy that she believes offers a better chance at success over the network television option. To her dismay, Katharine informs her that the idea has been dismissed, contrary to what Tess believed was positive feedback.
As Katharine prepares for a skiing getaway, she anticipates a marriage proposal from her boyfriend, Jack Trainer, portrayed by Harrison Ford. Shortly after Katharine departs, she suffers an injury on the slopes, calling Tess from the hospital with a slew of instructions to manage her workload. Intrigued by Katharine’s lavish home and belongings, Tess stumbles upon a tape recorder filled with Katharine's personal memos indicating that she valued Tess's idea, contrary to her prior dismissal. As tensions rise, Tess discovers a message directed to Jack, where Katharine claims Tess's proposal as her own.
Feeling betrayed, Tess finds herself at a crossroads when she discovers Mick in bed with another woman named Doreen. Disgusted and ready to make a change, Tess moves into Katharine's apartment, determined to reinstate her career using Katharine's credentials as leverage. With a newfound determination inspired by Katharine's earlier advice to take charge of her destiny, Tess arranges a meeting with Dewey Stone and Company, where Jack works, under the guise of an executive.
After a tense night at a party where she meets Jack under a false pretense and is mortified in the morning, Tess continues to present herself as an executive during business meetings. When Jack visits her on the trading floor, they solidify their bond, and yet Tess still wrestles with the duplicity of her situation. Despite their chemistry, she refuses to acknowledge her feelings for him, unwilling to mix business with personal matters.
As the merger progresses, Tess's double life becomes more complicated, especially during an engagement party where she encounters Mick and finally breaks free from that toxic relationship. However, during a critical meeting with Trask's executives, Katharine bursts in and reveals Tess's true role, throwing her under the bus. Infuriated, Tess attempts to defend her actions only to realize Katharine’s tactics have left her at a disadvantage.
Feeling defeated yet resolved, Tess edges closer to the truth about her talents through a climactic confrontation with both Jack and Katharine. She passionately lays out her business acumen, which ultimately wins over Trask, leading to an offer of an entry-level position at his company, fulfilling her dreams.
In the days following, Tess embarks on a new chapter, starting her job with Jack’s support at her side. As she arrives for her first day, she is pleasantly surprised to find that she will have a secretary named Alice, who is happy to assist her. Their rapport begins positively as Tess embraces her new role in the business world, triumphing in the long struggle for recognition and respect. She excitedly calls Cynthia to share her joy, signaling the beginning of a new, fulfilling career.
