Set during the Labor Day weekend of 1935, the novel weaves together the stories of three women whose lives intersect in the Florida Keys as a catastrophic hurricane bears down on them. Against the backdrop of the Great Depression, each woman faces a personal crisis that the storm transforms irrevocably.
Helen Berner is a waitress at Ruby's Café in Key West, heavily pregnant and trapped in a violent marriage to Tom, a fisherman she wed at sixteen. Tom has become controlling and abusive, and Helen privately fantasizes about his death at sea. Her only comforts are her unborn child and the routines of work, where Ruby, the café's owner, watches over her. A taciturn regular named John, a Great War veteran employed on a government highway project on the Keys, notices Helen's bruises but says little. Tom dismisses reports of a storm forming in the Bahamas, insisting the Weather Bureau says it will miss them.
Mirta is a young Cuban woman from a once-prominent Havana family whose fortunes collapsed after President Machado was ousted in 1933 and replaced by a regime backed by Fulgencio Batista. Her father arranged her marriage to Anthony Cordero, a wealthy Italian American with rumored ties to organized crime, for financial protection through Anthony's connections to Batista. Mirta and Anthony barely know each other, communicating awkwardly in English, their only shared language. They stop at Ruby's Café en route to a friend's beach house in Islamorada for their honeymoon before continuing to New York. Outside the café, Mirta and Helen share a candid conversation: Mirta tearfully confesses her anxiety about marrying a near stranger, and Helen offers hard-won wisdom about the exhaustion of bending to a husband's will.
Elizabeth Preston is a twenty-three-year-old former debutante from New York whose family was destroyed by the 1929 stock market crash. Her father and brother George both died by suicide in the aftermath, and Elizabeth supports her ailing mother, whose expensive medical treatments drain their meager resources. To pay off her father's debts to a dangerous mobster named Frank Morgan, Elizabeth agreed to marry him but has fled to the Keys with a letter from her estranged half-brother John, a veteran she hopes to find at one of the camps on the Keys. At Ruby's, Helen gives Elizabeth free pie and directions to the camps on Lower Matecumbe and Windley Keys, recommending her Aunt Alice's Sunrise Inn in Islamorada. Outside, a man named Sam Watson identifies himself as a Federal Bureau of Investigation (FBI) agent and offers to drive Elizabeth north. She accepts, reasoning that a federal agent's company could deter Frank's men.
That evening, two men attempt to rob Helen. John intervenes, and Helen strikes one attacker unconscious. John walks her home, describing his experience in the Bonus Army, a group of veterans who marched on Washington, DC to demand wartime service bonuses, only to be dispersed and forgotten. At the cottage, Tom is waiting, drunk. He grabs Helen by the wrist and neck and threatens to take the baby if she speaks to other men again.
On Sunday, Mirta and Anthony begin building genuine intimacy at the beach house. He refrains from consummating the marriage, telling Mirta he wants her to come to him willingly. Mirta discovers a gun in his nightstand and encounters a man in overalls lurking near the property. Elizabeth and Sam visit two veterans' camps, where conditions are appalling, but no one recognizes the photograph of Elizabeth's brother. A Coast Guard plane overhead trails a banner reading "Hurricane Warning."
Back in Key West, Ruby confronts Helen about Tom's abuse, urging her to leave. Helen's resolve crystallizes. With John's help and an advance from Ruby, she flees by ferry to Matecumbe Key, where Aunt Alice arranges for her to hide in a remote fishing cottage.
On Monday, Labor Day, the hurricane descends with devastating speed. Alone in the cottage, Helen's water breaks. John arrives, sent by Alice, and reveals he is a doctor who stopped practicing after the war because of trauma-induced tremors and flashbacks. He delivers the baby, whom Helen names Lucy, as the hurricane rages.
At the Islamorada train station, Elizabeth and Sam join a desperate crowd waiting for an evacuation train. A massive storm surge overtakes the train cars and sweeps them off the tracks. Elizabeth is struck by debris and nearly drowns. At the beach house, Mirta and Anthony shelter upstairs as floodwaters engulf the ground floor. The man Mirta saw lurking enters the bedroom with a knife, revealing he was sent by Frank Morgan. When Anthony returns and fights the intruder, Mirta grabs Anthony's revolver and kills the attacker. Anthony drags the body to the mangroves, and Mirta realizes her stolen engagement ring is gone with the dead man. In the fishing cottage, rising waters lift the structure off its stilts. Helen clutches Lucy while John holds them both as the cabin drifts through the night.
The aftermath reveals catastrophic destruction: bodies in trees, the railroad in ruins, entire communities erased. Elizabeth wakes in a Miami hospital, where Sam tells her the storm killed hundreds of veterans. Before the evacuation, Elizabeth had discovered photographs of herself among Sam's papers. Sam confessed that Frank hired him to follow her after she fled New York, though Sam is genuinely an FBI agent who infiltrated Frank's organization. Elizabeth feels deeply betrayed, though the hurricane forced them to set the argument aside.
Helen learns that Aunt Alice died in the storm, leaving her a life insurance policy and the land beneath the inn. Matthew, the inn's clerk, proposes they rebuild together. Mirta and Anthony are evacuated to Coral Gables, where Mirta demands Anthony abandon his criminal life. He presents her with a new engagement ring, and they consummate their marriage. In the hospital, Helen introduces Elizabeth to John, and Elizabeth recognizes him as the half-brother she traveled to find. Sam announces that Frank Morgan has been gunned down in New York, freeing Elizabeth from her engagement and her father's debts.
At a veterans' memorial in Miami, John tells Helen he plans to return to New York to support Elizabeth. Helen, heartbroken, says good-bye. John confesses he came to Ruby's all those months not for the pie but to see her. Elizabeth encourages John to pursue Helen. Elizabeth and Sam sleep together, choosing each other despite his deception.
On the train to New York, Sam approaches Mirta with a newspaper headline about Frank Morgan's murder, implying Anthony is responsible. In private, Mirta tells Anthony she does not need his confirmation and reiterates her expectation that he build a legitimate life for their family.
In April 1936, Helen narrates from the rebuilt Sunrise Inn. Sam arrives with John, now his brother-in-law, on FBI business and informs Helen that Tom's body has been found with a gunshot wound and an engagement ring in his pocket. Helen recognizes it as Mirta's stolen diamond but lies, saying she does not recognize it. After Sam departs, John stays. He has left the camps for good and asks if Helen could see herself building a life with him. Helen kisses him. The novel closes with her standing on the inn's porch, gazing at the sea, filled with hope for a future she once thought impossible.