The film unfolds over a single, intense day in the life of Jane, portrayed by Julia Garner, a junior assistant who has just begun her challenging role at a New York City film production company. After arriving before dawn, Jane dives into a series of monotonous yet essential administrative tasks, such as turning on lights, changing coffee filters, printing presentations, organizing office supplies, and even cleaning stains from her boss's couch. The relentless demands of her job create an atmosphere of stress that envelops her throughout the day.
During a phone conversation with her mother, Jane realizes she has neglected to call her father on his birthday—an oversight that weighs heavily on her mind. As the day unfolds, it becomes increasingly evident that her boss, Purva Bedi, is entrenched in a pattern of inappropriate behavior, engaging in sexual encounters with younger women within the confines of his office and perpetuating an environment rife with sexual harassment. The male executives make lewd comments regarding her boss's escapades, while the female staff are left to shoulder their responsibilities and discuss potential departmental transfers.
Each time Jane commits what her boss perceives as a mistake, he retaliates with abusive phone calls, all while her male co-workers, Jonny Orsini and Noah Robbins, watch in silence. Throughout Jane's day, various figures from her boss’s life make brief appearances—ranging from his wife to his children's nanny, a well-known actor, and a group of Chinese film producers.
Come afternoon, a newcomer named Sienna, played by Kristine Froseth, arrives from Idaho, claiming she has accepted a junior assistant position. Growing increasingly worried for Sienna's safety, Jane decides to report her concerns to the human resources department after dropping Sienna off at a luxurious company-paid hotel, a privilege that Jane herself never received. Alarmingly, Jane suspects that her boss is using Sienna as his latest fling, engaging in illicit "personal" affairs that take precedence over client meetings.
When Jane encounters Matthew Macfadyen, who plays the head of HR, he initially encourages her to voice her worries. However, he quickly backtracks, suggesting that Jane is overly sensitive, inferring that she is envious of the new assistant. His warning that filing a complaint could jeopardize her career further reinforces the toxic culture at play. As she departs his office feeling demoralized, he reminds her that she has nothing to fear because she isn’t his boss's "type."
Returning to her desk, Jane receives a call from her boss, who has been informed of her unfiled report. He demands an apology via email, which she reluctantly sends. Her boss later contacts her, claiming he is particularly hard on her to push her potential.
As the day comes to an end, Sienna drops by the office for a tutorial on the phone systems. With night approaching, Jane prepares a microwave dinner. While other employees exit the building, her boss lingers in his office with a young actress. Shortly thereafter, he instructs Jane through the intercom to head home. She chooses to visit a nearby coffee shop, where she calls her father while snacking on a muffin. Yet, as she hangs up, she catches a glimpse of a silhouette in her boss's office window that suggests an ongoing indiscretion.
