Louisa is a 28-year-old Englishwoman who moves to New York seeking new experiences following the death of a former client she loved. She works as a social secretary for the wealthy Gopnik family while attempting to adapt to a completely alien world of old money and strict social rules. Kind-hearted and highly adaptable, she possesses a passionate knowledge of vintage fashion. She strives to please her demanding employers while maintaining a long-distance relationship with her boyfriend back in England.

Sam is a paramedic back in England and Louisa's current boyfriend. He is recovering from a recent gunshot injury incurred at work and spends his off-time building a house from scratch. Generally reticent and diffident, he struggles to adapt to the geographic distance separating him from Louisa. He feels deeply self-conscious when viewing the wealthy, extravagant life his girlfriend now leads.

Mrs. De Witt is a cantankerous, fiercely independent resident of the Lavery. She is a former magazine fashion editor with a flamboyant, eclectic sense of style and a famously sharp tongue. Living alone with her pug, she initially appears hostile to her neighbors but possesses a vast collection of designer clothes and a deep understanding of self-expression.

Leonard is a multimillionaire belonging to a family of generational wealth. He resides in the highly exclusive Lavery building, an environment that only permits inherited ownership. While polite to his staff, he adheres strictly to traditional old-money conventions and expects his household to run seamlessly. He values social appearances and requires absolute discretion from his many employees.

Agnes is Mr. Gopnik's young, beautiful second wife. A Polish immigrant and former masseuse, she struggles to fit into the elite circles of New York's upper class. She frequently faces condescension from her peers and her husband's family. Volatile and defiant, she relies heavily on Louisa to navigate her highly structured new social life and manage her private affairs.

Kathryn is Leonard Gopnik's first wife. Coming from a similar wealthy background, she perfectly fits the mold of high society and retains the respect of her elite peers. She views loyalty and adherence to old-fashioned values as paramount, maintaining a frosty demeanor toward her ex-husband's new marriage.

Tabitha is Leonard Gopnik's daughter from his first marriage. A snobbish young woman in her early twenties, she deeply resents her father's second wife and makes no effort to hide her contempt. She views Agnes as a gold-digger and openly disparages the household staff.

Ilaria is the Gopniks' loyal housekeeper. While deeply devoted to Mr. Gopnik and the traditional functioning of the household, she detests Agnes and views her with intense suspicion. Beneath her strict exterior, she harbors a strong maternal instinct and looks out for vulnerable members of the staff.

Nathan is Mr. Gopnik's personal physical therapist and Louisa's friend who helped secure her job. Having managed the demands of the Gopnik household for some time, he understands their dispensability to the elite class and offers Louisa practical advice on how to survive in their demanding environment.

Ashok is the dedicated doorman at the Lavery. Warm, cheerful, and hard-working, he serves as a friendly face in an otherwise cold and isolated building. He works long hours to support his family, providing Louisa with her first glimpse into the working-class community of the city.

Meena is Ashok's fiery, strong-willed wife and mother to their three children. She is fiercely passionate about her community, actively participating in protests to save the Washington Heights neighborhood library from impending budget cuts.

Josh is a Bostonian who has recently moved to New York to work for a securities firm. Ambitious and polished, he belongs to an old-money family and frequently runs in the same elite circles as the Gopniks. He is quickly drawn to Louisa, but his most striking feature is his uncanny physical resemblance to her late love interest.

Will is Louisa's former client and late love interest. Though deceased, he continues to cast a long shadow over Louisa's life. She moved to New York based on his advice to seek new experiences, and she regularly reads old letters he sent to his mother detailing his own past time in the city.

Katrina is Louisa's younger sister back in England. She offers Louisa a grounding connection to home and provides regular updates about their family, as well as her own evolving romantic life.

Katie is Sam's new paramedic work partner. Her increasingly close presence in Sam's life, heavily documented on social media, quickly becomes a source of anxiety and insecurity for the geographically distant Louisa.

Steven is a local New York artist. Agnes commissions him for a last-minute charity art piece, which leads to her spending long, frequent hours in his studio under the pretense of taking art lessons.

Dean Martin is Margot De Witt's temperamental pug. He is Mrs. De Witt's sole regular companion, though his tendency to wander and occasionally bite causes friction in the Lavery.

Lily is Will Traynor's daughter. She stays in touch with Louisa via email, maintaining a link between Louisa and the memory of Will while sharing updates on her own life in England.

Garry is the Gopniks' driver. Surly and reticent, he chauffeurs Agnes and Louisa around the city, operating under a strict policy of seeing and hearing nothing in order to protect his employment.