The novel opens with a prologue set 13 years in the past. Fifteen-year-old Georgia Woodward walks into the home of her best friend, Adam Kim, and collides with Eli Mora, a recent transfer from Denver staying at his aunt's house after his father lost his job in the recession. Georgia and Eli feel an immediate connection, and he nicknames her "Peach." Georgia, whose mother left when she was three and whose public defender father is largely absent, has long treated Adam's household as a second home. She senses the three of them are becoming something special but foreshadows that she and Eli will go from best friends to lovers and burn it all down.
Thirteen years later, Georgia is 28 and working as a senior recruiting manager at a San Francisco tech company. Adam's wedding to his fiancée, Grace Song, is 10 days away. Georgia has handled nearly all the duties as best woman while Eli, now working at a New York investment bank, has been largely absent. Georgia's boss informs her that the company is dissolving her role and offering a director-level promotion in Seattle; if she declines, she loses her job, and she has until early September to decide. Her roommate and best friend, Jamie Rothenberg, recently moved to Oakland with her girlfriend, and Adam and Grace relocated to the suburbs, leaving Georgia increasingly isolated.
Adam FaceTimes Georgia, worried she and Eli are not truly okay, citing strange vibes at a mutual friend's wedding over a year earlier. Since their breakup five years ago, the two have maintained a careful performance for Adam's sake: limited eye contact, no touching, no meaningful conversation, no time alone. Georgia assures Adam everything is fine. At the airport the next day, she finds Eli disheveled, his phone conspicuously absent, staring at her far longer than their unspoken rules allow. He tries to start a serious conversation, but she deflects. In the car, he confesses he has been a terrible best man and asks to share the remaining responsibilities.
That evening, Grace arrives with devastating news: The wedding venue has burned down. Adam and Grace reveal that Grace is seven weeks pregnant, making postponement impossible. Adam proposes moving the wedding to Blue Yonder Winery, his mother's family's estate in Napa County. Both Georgia and Eli volunteer to handle preparations, and Adam sends them together. Georgia is privately horrified: Blue Yonder is where she and Eli spent formative summers and where their romantic feelings first ignited.
At a bakery appointment in Yountville, the baker mistakes them for the engaged couple and kicks them out after Eli arrives late from what he later reveals was a therapy appointment. They agree to split their task lists and stay out of each other's way. That agreement lasts barely a day. When Georgia accidentally knocks Adam's wedding band down the kitchen sink, Eli helps her retrieve it, and the shared relief triggers a genuine hug that nearly becomes a kiss. Eli tells Georgia she has to be the one to pull away because he cannot.
Monday night, the ceiling in Eli's cottage collapses, forcing him into Georgia's space. When he has a panic attack, he shares a grounding technique his therapist taught him, and Georgia walks him through it. He confesses he quit his job seven weeks ago, is not returning to New York, and is interviewing for a position in LA. Georgia processes the news with pride and pain, wondering why she was not enough to prompt this change five years earlier.
The physical tension escalates. They wake tangled together, and Georgia sets a three-minute limit on the encounter. At a second bakery, she impulsively tells the baker they are the engaged couple, selling the story with real memories. That evening in the pool, they negotiate terms: They will be together physically until everyone arrives on Friday, with no reckoning about the past. Eli warns that a reckoning will eventually come. They sleep together for the first time in five years.
Over the following days, they handle remaining wedding tasks. Adam's older cousin, Cole Cooper, the winery's director of sales, reveals he has been friends with Eli in New York over the past 18 months, a friendship Georgia knew nothing about. Cole privately warns Georgia to be careful. When Jamie arrives a day early on Thursday, Georgia proposes extending the physical arrangement through the wedding. That night, she throws a surprise bachelor party for Eli, who missed the original. He is visibly moved, understanding she is telling him he does not need to keep proving himself.
On wedding morning, Eli begins to tell Georgia something important, but Adam interrupts with cascading disasters: A fallen branch damaged the ceremony deck, the florist went to the wrong venue due to Georgia's error, and the officiant has food poisoning. Georgia picks up the cake but slips on wet pavement and smashes one side, then discovers her speech notebook is missing. She breaks down, and Eli calms her with the grounding technique. When Adam and Jamie arrive, Georgia confesses her deepest fears: that her friends will forget her as their lives progress, that she no longer fits. She reveals the Seattle job offer. They reassure her she is irreplaceable. Cole reveals he is ordained and can officiate.
The ceremony takes place in the rain under Blue Yonder's massive oak tree. Georgia delivers an improvised speech more honest than her prepared one. The reception is beset by mud and power outages, but the atmosphere is euphoric.
After the reception, Eli finds Georgia at the cottage and tells her he is in love with her, not just this week but always. He reveals that his date at the mutual friend's wedding was actually Cole's girlfriend doing him a favor, and that he left early because seeing Georgia hurt was unbearable. Georgia admits she wants to keep him but fears that needing him too much will destroy them again. Eli explains he chose to respect her decision to leave five years ago because he could not fix himself at the time. Georgia asks for friendship, arguing it is the safest way to keep him. Eli agrees reluctantly. They spend one last night holding each other. In the morning, he is gone, leaving a paper ring on her nightstand.
Georgia accepts the Seattle promotion and moves into her own apartment. She resumes therapy, builds new friendships, and maintains a warm but boundaried friendship with Eli. On the night before her birthday, she spills wine on the paper ring and discovers handwriting inside: a numbered entry in a list of reasons Eli loves her. She unravels every paper ring she has saved over 13 years and finds entries spanning their entire history. The final entry reads: "Because you don't want me to say goodbye this morning. You don't know yet that with us it's never goodbye. But you will, I promise" (339). Eli's love has been constant, and Georgia realizes her refusal to be vulnerable has been the real barrier.
Adam calls to say someone is at her door. Eli stands there with a cupcake and a candle, echoing the birthday tradition that preceded their first exchange of "I love you." Georgia tells him she loves him and hates being just his friend. In their long-deferred reckoning, Eli explains that Georgia was the catalyst for quitting his job: When promoted to VP, he realized he was on track to become his lonely, workaholic boss. He turned down both the LA and San Francisco offers and chose to come to Seattle, to her. They commit to honesty, messiness, and each other.
In the epilogue, set eight months later, Georgia and Eli marry at Blue Yonder during a trip for Adam and Grace's baby Penny's 100-day celebration. Cole officiates, their loved ones surround them, and the novel ends with Georgia and Eli jumping hand in hand into the pool, an echo of the summers where their love began.