The novel unfolds across two timelines, alternating between present-day events and flashbacks that trace the complicated history between Eve Keller and Madden Donahue in the small Rhode Island town of Cumberland.
When 14-year-old Eve meets 16-year-old Madden at the home of her best friend, Skylar Page, she feels an immediate connection to the quiet, guarded boy who has recently arrived from Ireland to live with his Aunt Fiona next door. Madden is the first person Eve's age who does not mock her for her father's ownership of Cat Fight, a local strip club. Skylar confesses a crush on Madden, and Eve suppresses her own feelings, silently vowing never to compete with her only real friend, a sacrifice that defines the next eight years of her life.
A flashback reveals why Madden left Ireland. He is not his father's biological child, and his father directed years of physical abuse exclusively at him. Madden asks his Aunt Fiona, herself once driven from Ireland by family cruelty, to let him stay permanently, and she agrees. At Cumberland High, Madden appoints himself Eve's protector, physically confronting older boys who harass her about her father's club.
Two years later, Eve notices Madden losing weight and struggling to breathe. She forces him to the hospital, where doctors diagnose him with polycystic kidney disease, a condition that impairs kidney function. An anonymous donor offers a kidney, and Madden accepts the transplant. Eve visits him days after surgery looking pale and weak, claiming she has the flu. The narrative implies that Eve is recovering from donating her own kidney to save his life, a secret she guards for years.
In the present day, 22-year-old Eve is raising her five-year-old niece and nephew, Lark and Landon, after her older sister Ruth entered rehab for addiction. Eve also runs the Gilded Garden, a burlesque club she converted from her father's former strip club, but the business is failing. When Madden appears at her apartment, he announces he has been signed by the New York Yankees and insists they need to talk.
A flashback to four years earlier shows the first time Madden makes his romantic interest explicit. At Skylar's graduation party, he asks Eve to dance and begins confessing deeper feelings, but Skylar interrupts and Eve vanishes, continuing a pattern of retreat. In the present, Madden confronts Eve about the real reason she has kept him at a distance: Skylar's crush. Eve admits she has always had feelings for him but calls herself a worse choice than Skylar. Madden refuses to accept this, embraces her fiercely, and leaves with a promise to return.
Eve's situation grows more urgent when Landon is diagnosed with asthma, adding expensive medical needs to an already strained budget. A young musician named Veda walks into the club and quickly becomes Eve's confidante and business partner, pitching an idea to build an outdoor music venue called the Jam Jar on unused land behind the club. Veda confides that her boyfriend and bandmate, Smith, stifles her creativity, refusing to let her sing lead or add her original songs to their setlist.
After learning that Skylar's crush on Madden has been replaced by a serious relationship with hockey player Robbie Corrigan, Eve agrees to marry Madden under strict conditions: The marriage stays secret, lasts six months, and exists solely to provide health insurance for the children. Madden agrees, privately resolving to spend those months convincing her the marriage should be permanent. They share their first kiss, negotiate a "friends with fulfillment" arrangement in which Eve can explore her exhibitionist desires exclusively with him, and marry at a courthouse with Skylar's stepbrother, Elton Page, and Veda as witnesses.
Their physical relationship escalates during Madden's visits to Cumberland. Eve reveals this is her first sexual experience; she trusted no one else. Shaken by the depth of their connection, Madden declares the six-month limit is off. Eve panics, but he drives away before she can argue.
In New York, Madden begins finding his voice among his teammates. After calling them "overpriced fucking crybabies" and absorbing a punch from pitcher Ruiz, the two develop a genuine rapport. Madden advises Ruiz to rediscover his love for the game, and Ruiz starts following Madden's pitch calls, producing his best performance in years. When Eve, Skylar, Veda, and Elton attend a game, a runner collides with Madden at home plate. He holds onto the ball despite the brutal impact, winning the game but injuring his shoulder. The clip goes viral, earning him the nickname "Bad Madden."
Eve spends the night at Madden's Manhattan apartment. They imagine a future together, complete with purple Christmas lights on their balcony, and Madden tells Eve he loves her. She does not say the words back but communicates her feelings through her trust and presence. The next morning, Eve overhears Madden on the phone with Yankees management, who express concern about how her profession reflects on the organization. Terrified that her reputation will damage his career, she flees. Madden chases her to the lobby, where paparazzi have gathered, and kisses her in front of the cameras, declaring her his wife. Eve drives back to Rhode Island, devastated.
The media frenzy intensifies, with tabloid headlines cheapening Eve's profession and fabricating details about their relationship. Ruth arrives unexpectedly, healthy after completing her treatment program, and takes the twins to a supported housing program in North Carolina. Reeling from the loss of the children and the media scrutiny, Eve decides to perform at the club that night, partly to reclaim control and partly to sabotage her image as a respectable wife, thereby freeing Madden. Backstage, Smith shoves Veda for showing off onstage, and Elton violently intervenes, revealing the depth of his feelings for Veda.
Madden arrives during Eve's performance and sees her kidney donation scar for the first time, exposed by her costume. Rather than stopping her act, he walks onstage, removes his shirt, and joins the performance, supporting her reclamation rather than undermining it. He unfastens her bra at her request, and they stand chest to chest before he carries her offstage to thunderous applause.
Backstage, Eve finally lets her walls fall. She tells Madden she loves him, confesses the full story of the donation, and accepts that their love is permanent. The next morning, an article titled "Bad Madden & the Girl Who Saved His Life" has gone viral. Madden reveals he plans to renovate his aunt's house into a home for Ruth and the twins. Eve insists on breakfast at a local diner, a simple act she has never felt comfortable doing in Cumberland. When they walk in, the patrons break into applause. Rather than taking this acceptance as a reason to stay, Eve tells Madden it proves she has nothing left to prove. She sells the Gilded Garden to Veda for one dollar down and moves to New York with Madden.
An epilogue set seven years later finds them in Wisconsin, where Madden plays for the Brewers. Their home is decorated with purple Christmas lights, the tradition they imagined during their first night together in Manhattan. Eve has earned a business degree and started a commercial interior design firm called Gilded. The Gilded Garden thrives under Veda's ownership. Skylar, Robbie, and their baby visit, along with 12-year-old Lark and Landon. Madden watches Eve through the kitchen window, then walks inside to her greeting, content in the knowledge that this life, built on years of patience and devotion, is permanent.