On a hot June day, three women and two small children arrive on Nantucket Island, observed by Josh Flynn, a twenty-two-year-old airport ramp attendant and creative-writing student at Middlebury College. The women are sisters Vicki Stowe and Brenda Lyndon, along with Vicki's friend Melanie Patchen, and each carries a burden she hopes the summer will ease.
Vicki, mother of four-year-old Blaine and nine-month-old Porter, has been diagnosed with stage-two lung cancer and plans to undergo chemotherapy at Nantucket's small cottage hospital rather than a major medical center, a decision her husband, Ted Stowe, a hedge-fund manager, opposes. Brenda, a literature professor, has been fired from Champion University for sleeping with her student, a thirty-one-year-old Australian named John Walsh, and faces criminal charges for accidentally damaging a university-owned Jackson Pollock painting. Melanie has fled home after discovering that her husband, Peter Patchen, is having an affair with his colleague Frances Digitt. She is secretly pregnant after seven failed rounds of in vitro fertilization and has told no one, including Peter. They settle into Aunt Liv's cottage in the village of 'Sconset, a tiny house Vicki and Brenda recently inherited. Their mother has always believed that Nantucket sand between the toes can cure any ailment, and the summer is meant as a refuge.
Tensions surface immediately. Brenda panics when she realizes she left behind a briefcase containing her priceless first-edition copy of Fleming Trainor's novel
The Innocent Impostor. Josh finds the briefcase and delivers it to the cottage, establishing his first connection with the household. A terrifying incident soon follows at the beach: Vicki asks Melanie to watch Blaine, but Melanie, lost in thoughts of Peter, loses track of the boy. After a ninety-minute search involving police and ATVs, Blaine is found over a mile down the beach, calmly throwing rocks. The episode deepens Melanie's self-doubt about her fitness as a mother. That Sunday, Melanie attempts to flee the island but cannot get a flight. Josh gives her a ride back, and during the drive she impulsively tells him she is pregnant.
When Vicki begins chemotherapy, Brenda manages the children alone at the hospital and encounters Josh again. Needing a babysitter, she hires him at twenty dollars an hour, five mornings a week, and he quits his airport job. Josh quickly becomes the household's stabilizing presence, taking Blaine and Porter to the beach each weekday and earning the boys' fierce devotion. Blaine imitates Josh's clothing and declares him his best friend. Porter, who had refused bottles since being weaned, begins taking them from Josh. Josh's emotional investment grows as he recognizes that the boys face the possibility of losing their mother, mirroring the loss of his own mother, who died by suicide when he was twelve.
Vicki's chemotherapy takes a severe toll. She loses weight and hair, and becomes too weak to leave bed for days. One morning she refuses treatment, telling Brenda the drugs are killing her. Josh confides to Vicki about his mother's death and tells her that if she stops treatment and dies, leaving her boys motherless, he will hate her. Vicki relents. Brenda, overwhelmed with gratitude, kisses Josh in the front yard but immediately pulls back and tells him she is in love with someone else. Melanie witnesses the kiss from down the street.
Meanwhile, Brenda struggles to write a screenplay adapted from
The Innocent Impostor, her only hope of earning the one hundred and twenty-five thousand dollars her lawyer, Brian Delaney, Esquire, has negotiated as settlement for the damaged painting. She discovers she can only write productively in the oncology waiting room while Vicki receives treatment. Extended flashbacks detail her affair with Walsh: their first meeting in class, their first date at the Cupping Room bar, and its exposure when a colleague saw them together and a jealous student raised concerns, leading to Brenda's dismissal.
Ted arrives for weekends, bringing supplies and marital friction. The couple's sexual relationship has collapsed: Ted cannot perform, which Vicki interprets as revulsion and Ted attributes to paralyzing fear of losing her. One night Vicki walks alone to Sankaty Head Lighthouse, tells Ted she is going to die, and he carries her home.
At a family beach picnic at Smith's Point, the household shares lobster, a bonfire, and fishing. After the others go to bed, Melanie taps on Josh's Jeep window and they walk to the garden behind the 'Sconset Chapel, where they kiss. When Josh hesitates at her pregnant belly, she presses his hands there, and he kisses her stomach. A secret nightly affair begins, with Melanie climbing out her window each evening to meet Josh at secluded spots around the island. Josh's ex-girlfriend Didi, who works at the hospital's admitting desk, learns of the affair through her brother and attempts to blackmail Josh, but he refuses.
Vicki's health reaches a crisis when her white blood cell count plummets and she develops a dangerous fever lasting five days. Treatment is deferred, then resumed at a lower dosage. Gradually Vicki improves, and a CT scan reveals the tumor has shrunk significantly. Dr. Garcia, her surgeon, schedules an operation for September 1. Melanie calls Peter from a pay phone and tells him she is pregnant; he is stunned but amazed, and she hangs up feeling in control for the first time.
Peter then arrives unannounced on Nantucket, declaring his affair over and begging Melanie to return. She tells him there is someone else but refuses to say who. The next morning, Josh arrives to find Peter at the kitchen table. Shattered, Josh tells Melanie they should end things, and their nightly meetings cease.
Days later, Vicki collapses after weeks of secretly self-medicating with escalating doses of painkillers for debilitating headaches. In the ambulance, she silently communicates her deepest wish to Brenda: that Brenda raise Blaine and Porter if Vicki dies. Brenda squeezes her hand and says, "Okay." An MRI reveals no brain metastases; doctors determine Vicki overmedicated.
The final days bring arrivals and departures. Ellen and Buzz Lyndon, Vicki and Brenda's parents, arrive from Philadelphia. Walsh appears, having driven through the night after Brenda called him from the hospital, and Brenda dissolves in his arms, realizing love is all that matters. Separately, Didi dies from an accidental overdose. Josh attends her funeral, then drives to the cottage for a final dinner. He reads Blaine
Sylvester and the Magic Pebble and kisses both boys goodnight without saying goodbye.
Brenda finishes her screenplay and calls Ron Feldman, president of Marquee Films and father of a former student, to pitch it. Ron flatly rejects the idea. However, as Brenda and Walsh leave the island, her lawyer calls: Ron has reconsidered, read
The Innocent Impostor, and wants to see the screenplay, with a possible five-figure option. Brenda, who sprinkled sand from her mother's jar into her shoes before departing, feels she is already over the moon.
The epilogue, set the following winter, reveals outcomes. Melanie gives birth to a daughter, Amber Victoria, and is back together with Peter, but she receives an unsigned card reading, "I know she's beautiful," clearly from Josh, and cries with longing for the summer. Vicki, five months post-surgery, is cancer-free but profoundly changed, living in wonder and gratitude. Brenda, working at a bookstore and living with Walsh, has her screenplay in circulation. Whatever comes next, she is ready.