The novel follows Julie Pike, a 43-year-old wife and mother of two grown daughters, whose comfortable suburban life collapses when her husband reveals he has been unfaithful.
Julie stands in her large Atlanta home, saying goodbye to Agnes, her longtime housekeeper, as she prepares for a new chapter. Her daughters are both away: Meg, 19, studies abroad in France, and Colleen, 20, interns at a law firm in California. Julie and her husband of 21 years, Michael, have put a contract on a beach cottage along the South Carolina coast, fulfilling Julie's lifelong dream. Michael plans to retire after one last business trip, and Julie will run her online boutique from the new home.
That evening, Michael returns over three hours late, irritable and evasive. He announces he is leaving Julie for a woman named Victoria in Boston, revealing they have a six-month-old son named Charlie. Michael always wanted a son, but Julie refused more children after two difficult pregnancies, a decision that caused a lasting rift. He tells Julie the beach house deal is off, that their Atlanta home sale will close in three weeks, and hands her keys to a prepaid hotel suite. Julie is shattered.
The following weeks blur with grief. Meg calls, distraught after Michael tells her; Julie insists both daughters stay where they are. Colleen reveals Michael is already engaged to Victoria. At the house closing, Julie encounters Victoria holding Charlie in the parking lot. She tells Victoria that what a man does with one woman, he will eventually do to her, and drives away in tears.
A lunch with her wealthy country-club friends proves hollow. Mallory, Tiffany, and Heidi focus on Julie's social standing rather than her pain. Julie snaps, realizes she does not want to become like these women, and decides to leave town.
Julie uses her share of the house sale proceeds to buy a cottage sight unseen on Seagrove Island, a tiny South Carolina island with about 100 residents. The exterior is charming, set on marshland under moss-draped trees, but the interior is in shambles: holes in the floors, no electricity, no bed. She walks onto the back porch, watches a stunning sunset over the marsh, and weeps.
Searching for shelter, Julie finds Lancaster House, a 1918 home at the island's other end with an "open" sign in the window. Dawson Lancaster, her new neighbor, takes Julie in for the night along with his housekeeper, Lucy. He reveals the inn has not operated since his grandmother ran it in the 1980s; the sign stays lit in her honor. He refuses payment, tells Julie the island "never lets anyone go," and gives her his business card before she leaves.
Julie camps in her cottage with an inflatable mattress and battery-powered fans. Two contractors quote prices she cannot afford. When Dawson arrives for a scheduled estimate, he reveals he owns Seagrove Contracting, quotes half the price, and estimates three months of work. Julie accepts, and a friendship forms.
Her mother, SuAnn, arrives unannounced with Julie's estranged older sister, Janine. The sisters have not spoken in years, their relationship fractured when Janine gave unsolicited life advice to Julie's teenage daughters. SuAnn pressures them to reconcile, mentioning "anomalies" on her recent blood work. Julie reluctantly lets Janine stay.
Janine appears subdued and unlike her formerly vivacious self. After a heated argument, she reveals that two years earlier she was attacked while walking to her bungalow after teaching a yoga class in the Caribbean. She has told no one. The trauma caused her to stop teaching, lose her job, and develop an eating disorder. Julie insists the attack was not Janine's fault and promises to find her counseling.
Julie also meets Dixie, the colorful owner of Down Yonder Books on the mainland, who becomes a genuine friend. Dixie shares her own losses: Her youngest son died in a hunting accident, her husband died of cancer, and her older son, William, blamed Dixie and has not spoken to her in over 10 years. Julie takes a part-time job at the bookstore. Through Dixie, she learns about a local author who published her first novel at nearly 70, inspiring Julie to revisit her childhood dream of writing.
Dawson shares his own painful history: His wife, Tania, died from uncontrollable bleeding after going into premature labor, and their newborn son did not survive. His brother later died of a stress-related heart attack. Despite these losses, Dawson remains kind and grounded, advising Julie not to waste her second chance with Janine.
The sisters' relationship slowly improves. Janine begins counseling and starts recovering. She teaches Julie a yoga class, earning new respect. During a climb to a platform Dawson built as a child in a live oak tree, the sisters acknowledge their mutual jealousy: Julie envied Janine's adventurous life, while Janine envied Julie's stability and family. Julie confides she has begun writing a novel, and Janine reveals she is considering starting a yoga business for trauma survivors.
A process server delivers divorce papers, and Janine discovers that Michael secretly purchased a condo in Boston with marital funds. She urges Julie to fight for her share, but Julie wants to move forward.
A nurse calls from Boston: Michael has been in a serious car accident and is in grave condition. As his legal next of kin, Julie flies to Boston with Janine to make medical decisions. Victoria visits the hospital only once and tells staff she is not interested in caring for someone with debilitating injuries. Julie commits to staying at Michael's bedside for her daughters' sake. Michael eventually wakes, confused and calling for Victoria. Dawson sends Julie a care package of Southern food with a heartfelt note saying everyone misses her.
Abandoned by Victoria, Michael suggests he and Julie reconcile. Julie does not want him back but agrees to explore transferring his rehabilitation to Seagrove so she can return home. Dixie warns that "scoundrels rarely change." The night before they are to leave, Julie overhears Michael on the phone with Victoria, telling her he loves her and plans to return to Boston once he recovers. Julie arranges alternative care, tells their daughters the truth, and informs Michael he is no longer her responsibility.
Julie returns to Seagrove and walks through the fully renovated cottage, overwhelmed by its beauty. She finds Dawson on her bench by the marsh; he pulls her into a hug. Julie acknowledges she has feelings for him, asks him to dinner, and implies it is a date. He accepts.
The epilogue takes place at Christmas. Julie hosts dinner with Janine, Dawson, SuAnn, SuAnn's husband, Buddy, and Dixie. Her divorce is final, and she and Dawson are dating slowly. Julie confronts SuAnn about the health scare, having learned the "anomalies" were simply high cholesterol; SuAnn admits she fabricated the concern to force her daughters to reconcile. As the family sits down to dinner, there is a knock at the door. Julie opens it to find William, Dixie's estranged son, asking for his mother. The novel ends with Julie embracing the truth that new beginnings, though bumpy, are worth it.