The Carmichaels and the Grahams have gathered on Nantucket for a wedding. Plans are being made according to the wishes of the bride's late mother, who left behind The Notebook: specific instructions for every detail of her youngest daughter's future nuptials. Everything should be falling into place for the beautiful event - but in reality, things are far from perfect. While the couple-to-be are quite happy, their loved ones find their own lives crumbling.

Hollis Shaw, creator of the popular food blog, Hungry with Hollis, is shocked when her heart surgeon husband, Matthew, is killed in a one-car accident on a snowy morning. The cracks in Hollis’s perfect life—her strained marriage and her complicated relationship with her daughter, Caroline—grow deeper. So when Hollis hears about something called a “Five-Star Weekend”—one woman organizes a trip for her best friend from each phase of her life: her teenage years, her twenties, her thirties, and midlife—she decides to host her own Five-Star Weekend on Nantucket.

From marriage, infidelity, and the mayhem of motherhood to scandal, tragedy, and illness - three women seek peace and comfort in Nantucket as they cope with life's challenges. Three women - burdened with small children, unwieldy straw hats, and some obvious emotional issues - tumble onto the Nantucket airport tarmac one hot June day. Vicki is trying to sort through the news that she has a serious illness. Her sister, Brenda, has just left her job after being caught in an affair with a student. And their friend Melanie, after seven failed in vitro attempts, is pregnant at last.

Welcome to the most tumultuous summer of the 20th century. It's 1969, and for the Levin family, the times they are a-changing. Every year, the children have looked forward to spending the summer at their grandmother's historic home in downtown Nantucket. But like so much else in America, nothing is the same.

Claire has a problem with setting limits. All her life she has taken on every responsibility, assumed every burden, granted every request. Claire wants it all—and in the eyes of her friends, she has it: a devoted husband, four beautiful children, even a successful career as an artist. So when she agrees to chair the committee for Nantucket's social event of the year, she knows she can handle it. Claire can handle anything. But when planning the gala propels her into the orbit of billionaire Lock Dixon, unexpected sparks begin to fly.

Kelley Quinn is the owner of Nantucket's Winter Street Inn and the proud father of four, all of them grown and living in varying states of disarray. Patrick, the eldest, is a hedge fund manager with a guilty conscience. Kevin, a bartender, is secretly sleeping with a French housekeeper named Isabelle. Ava, a school teacher, is finally dating the perfect guy but can't get him to commit. And Bart, the youngest and only child of Kelley's second marriage to Mitzi, has recently shocked everyone by joining the Marines.

On a perfect June day, Vivian Howe, author of 13 beach novels and mother of three nearly grown children, is killed in a hit-and-run car accident while jogging near her home on Nantucket. She ascends to the Beyond where she's assigned to a Person named Martha, who allows Vivi to watch what happens below for one last summer. Vivi also is granted three “nudges” to change the outcome of events on earth.

Celebrity chef Deacon Thorpe has always been a force of nature with an insatiable appetite for life. But after that appetite contributes to Deacon's shocking death in his favorite place on earth, a ramshackle Nantucket summer cottage, his (messy, complicated) family is reeling. Now Deacon's three wives, his children, and his best friend gather on the island he loved to say farewell.

When Mallory Blessing's son, Link, receives deathbed instructions from his mother to call a number on a slip of paper in her desk drawer, he's not sure what to expect. But he certainly does not expect Jake McCloud to answer. It's the late spring of 2020 and Jake's wife, Ursula DeGournsey, is the frontrunner in the upcoming Presidential election. There must be a mistake, Link thinks. How do Mallory and Jake know each other?

Nantucket is only 11 miles away from Martha's Vineyard. But they may as well be worlds apart for estranged twin sisters Harper and Tabitha Frost. After not speaking for more than a decade, Harper and Tabitha switch islands - and lives - to save what's left of their splintered family. But the twins quickly discover that the secrets, lies, and gossip they thought they'd outrun can travel between islands just as easily as they can. Will Harper and Tabitha be able to bury the hatchet and end their sibling rivalry once and for all?