Set in the early 1900s, the novel follows three women whose lives converge around the creation of the Colony Club, the first social club for women in New York City. The story is framed by scenes set on April 18, 1963, where 92-year-old Daisy Harriman, the first recipient of President Kennedy's Citation of Merit for Distinguished Service, reflects on her career for a young journalist named Meg. When asked what first inspired her to step into public life, Daisy answers that it all began one summer when she could not get a room at the Waldorf.
In August 1902, Daisy, a young society matron in Newport, Rhode Island, is furious that the Waldorf Hotel has refused to accommodate her because she is an unaccompanied woman. Her husband, Bordie, a banker, has multiple men's clubs where he can stay comfortably, but women have no equivalent. The injustice sparks an idea: Women should have a club of their own, with overnight rooms, dining, and social amenities. Daisy recruits across Newport society and hosts a planning tea where the attendees settle on the name "the Colony Club." Over the next two years, the women form a steering committee and secure financing through a men's advisory board organized by J. P. Morgan, the powerful banker and father of club member Anne Morgan. In January 1903, Daisy and Anne sign papers for property at 120–124 Madison Avenue.
The narrative introduces Nora Bromley, a poor but determined architecture student at the New York School of Applied Design for Women. Nora funds her tuition with money her father set aside before he died, money originally intended for her older brother, Jimmy, who died of tuberculosis. Jimmy's death left Nora carrying his dream of designing buildings that would help people and a deep sense of obligation to her family. Every Sunday she visits her family in Brooklyn: her resentful older sister Louise, Louise's husband Donner, her aging mother, and her younger sister Rina. Louise resents Nora for receiving the education meant for Jimmy, and Nora turns over most of her meager tutoring income for the family's expenses.
The novel also introduces Elsie de Wolfe, an actress whose role in a hit play earns her tepid reviews despite her reputation as the best-dressed performer on the Rialto, as Manhattan's theater district is known. Daisy attends the play and afterward resolves to enlist Elsie's companion, Bessie Marbury, the most formidable theatrical agent in New York, to convince the celebrated architect Stanford White to design the Colony Club. Bessie assures Daisy she will secure White's commitment, noting that the financially overextended architect cannot afford to refuse.
In April 1904, Nora enters a design competition with a hospital for tuberculosis patients inspired by Jimmy's illness, incorporating natural light and an innovative layout. Stanford White serves as a judge, and Nora wins first place. White offers her rendering work at his firm, McKim, Mead, and White. When Nora arrives, George Douglas, a young architect and White's assistant, helps her navigate the hostility of the all-male office and escorts her to White, who agrees to hire her on trial. Nora is given a drafting desk in the back corner of the drafting room, segregated from roughly 50 male draftsmen.
Nora endures months of escalating harassment led by Collin Nast, a draftsman whose desk she must pass daily. Her stool is stolen, her drafting table overturned, and her tools regularly disappear. A draftsman named Fergus Finnegan becomes her first ally. She also befriends the secretaries, particularly Miss Higgins, the bookkeeper everyone calls Higgie, who becomes her closest confidante.
White assigns Nora to create a presentation watercolor of the Colony Club facade, but Nast engineers an accident that destroys her nearly finished rendering. Nora stays through the night and completes a second version. White later assigns her to the clubhouse project full-time at the construction site. Though initially devastated to leave prestigious projects, Nora is moved when she first sees the brick pattern she drafted rendered in reality and whispers, "We're here, Jimmy." The foreman, Mr. Wojcik, becomes an enthusiastic mentor. George regularly takes Nora for tea at a nearby café, and a quiet bond develops between them.
Meanwhile, Daisy faces persistent opposition from clergy, moralists, and husbands who try to discredit the club. She receives a delegation that includes a representative of Anthony Comstock's Society for the Suppression of Vice, a group dedicated to policing public morality, but counters every argument and refuses to concede.
In January 1905, Bessie proposes hiring Elsie to design the Colony Club's interior, since White is overextended. White endorses the plan, and Elsie, whose theater career has been fading, embraces the opportunity as her new calling. Bessie tells Elsie she could become America's first female interior decorator. When White assigns Nora as Elsie's assistant, Nora is furious, viewing the work as beneath real architecture. George confronts her, and Nora breaks down, revealing the weight of her brother's unfulfilled dreams and her promise to her family. George tells her he believes in her future.
Nora begins translating Elsie's sketches into professional renderings while Elsie departs on buying trips to Europe. Mrs. Harriman invites Nora to attend club lectures on child labor, garment workers' conditions, and tuberculosis. After hearing a lecture on sweatshop conditions, Nora sketches a design for a safer factory, which Mrs. Harriman encourages her to develop. When Elsie returns, she presents her designs to the decoration committee and, through theatrical persuasion, wins over ladies who initially find the rooms too plain, arguing that the club should serve women's comfort rather than replicate dark, stuffy men's clubs.
On June 25, 1906, Stanford White is murdered by Harry K. Thaw, a jealous husband, at the Madison Square Garden rooftop theater. Collin Nast points Nora out to reporters outside the firm's building, calling her White's "personal assistant." Her photograph appears in the
New York Evening Journal alongside lurid insinuations. The fallout is swift: Her roommates pressure the hotel to evict her, and Louise bars Nora from her home. Homeless, Nora sleeps on the floor of the construction office until Higgie insists Nora stay at her brownstone with her Aunt Sorcha, a progressive activist. Nora discovers a life she never imagined: a room of her own, hot baths, and generous meals.
The Thaw murder trial dominates headlines into 1907. Protesters gather outside the Colony Club, and J. P. Morgan and the men's advisory committee urge the women to sell the property to the Princeton Club and dissolve. Daisy tears the purchase contract in half, declaring they will not sell. Bessie and Elsie devise a media strategy, placing articles in prominent publications that spotlight Elsie's innovative design rather than the scandal.
The Colony Club Grand Opening takes place in early 1907. Elsie leads guests through the marble swimming pool with its fairy-light grapevine ceiling, the trellis room, the gymnasium, and the assembly hall. The evening is a triumph. That night, George finds Nora and proposes a business partnership: He and Fergus are leaving the firm to start Finnegan, Douglas, and Bromley, with Nora as a full partner. When she asks if her name will really be on the sign, George promises it will always say "Bromley," even if she someday takes his name. Nora accepts.
A brief epilogue set in November 1909 shows Nora and George, now married, reading that the Colony Club ladies have joined striking garment workers on the picket line in their mink coats. The press dubs them the "Mink Brigade." The novel closes with the 1963 frame, where Daisy reflects that most of her friends are gone but concludes: "By their energy, skill, and dedication to so many causes, and through the lives they changed, they are all very much alive."