Birdie Cousins has thrown herself into the details of her daughter Chess's lavish wedding, from the floating dance floor in her Connecticut back yard to the color of the cocktail napkins. Like any mother of a bride-to-be, she is weathering the storms of excitement and chaos, tears and joy. But Birdie, a woman who prides herself on preparing for every possibility, could never have predicted the late-night phone call from Chess, abruptly announcing that she's cancelled her engagement. It's only the first hint of what will be a summer of upheavals and revelations.

Everyone refers to the St. Cecelia as “the Saint.” If you grew up coming here, you were “a Saint.” If you came from the wrong side of the river, you were “an Ain’t.” Traci Eddings was one of those outsiders whose family wasn’t rich enough or connected enough to vacation here. But she could work here. One fateful summer she did, and married the boss’s son. Now, she’s the widowed owner of the hotel, determined to see it return to its glory days, even as staff shortages and financial troubles threaten to ruin it. Plus, her greedy and unscrupulous brother-in-law wants to make sure she fails.

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.

Kezia Cooper Hobson, recently widowed, arrives in New York from San Francisco. Determined to make a fresh start, she has just completed the sale of her Pacific Heights home, not to mention her husband's venture capital firm, and in doing so, is also freed from her responsibility as a board member of the company. Bringing with her only a few personal treasures, she is excited to move into the blank slate of a beautiful midtown penthouse, in the city that she has always loved. It is also where her two adult daughters now live.

Finola, a popular LA morning-show host, is famously upbeat until she’s blindsided on live TV by the news that her husband is sleeping with a young pop sensation. While avoiding the tabloids and pretending she’s just fine, she’s crumbling inside. Zennie’s breakup is no big loss. Although the world insists she pair up, she’d rather be surfing. So agreeing to be the surrogate for her best friend is a no-brainer. Ali is used to being overlooked, but when her fiancé sends his disapproving brother to call off the wedding, it’s a new low.

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.

Years of trying unsuccessfully to conceive a child have broken more than Angie DeSaria’s heart. Following a painful divorce, she moves back to her small Pacific Northwest hometown and takes over management of her family’s restaurant. In West End, where life rises and falls like the tides, Angie’s fortunes will drastically change yet again when she meets and befriends a troubled young woman.

For 18 years, Jude Farraday has put her children’s needs above her own, and it shows - her twins, Mia and Zach, are bright and happy teenagers. When Lexi Baill moves into their small, close-knit community, no one is more welcoming than Jude. Lexi, a former foster child with a dark past, quickly becomes Mia’s best friend. Then Zach falls in love with Lexi and the three become inseparable. Jude does everything to keep her kids on track for college and out of harm’s way. It has always been easy - until senior year of high school. Suddenly she is at a loss.

Ava thinks love should be found in the real world, not on apps that filter men by height, job, or astrological sign. She believes in feelings, not algorithms. So after a recent breakup and dating app debacle, she decides to put love on hold and escapes to a remote writers' retreat in coastal Italy. At the retreat, she's not allowed to use her real name or reveal any personal information. When the neighboring martial arts retreat is canceled and a few of its attendees join their small writing community, Ava, now going by "Aria", meets "Dutch", a man who seems too good to be true.

Adrienne Dealey has spent the past six years working for hotels in exotic resort towns. This summer she has decided to make Nantucket home. Left flat broke by her ex-boyfriend, she is desperate to earn some fast money. When the desirable Thatcher Smith, owner of Nantucket's hottest restaurant, is the only one to offer her a job, she wonders if she can get by with no restaurant experience. Thatcher gives Adrienne a crash course in the business...and they share an instant attraction.

Once upon a time, when her dad married Sage’s mom, Daisy was thrilled to get a bright and shiny new sister. But Sage was beautiful and popular, everything Daisy was not, and she made sure Daisy knew it. Sage didn't have Daisy's smarts—she had to go back a grade to enroll in the fancy rich-kid school. So she used her popularity as a weapon, putting Daisy down to elevate herself. After the divorce, the stepsisters' rivalry continued until the final, improbable straw: Daisy married Sage's first love, and Sage fled California.

After uprooting her life in the States, Irene Steele has just settled in at the villa on St. John where her husband Russ had been living a double life. But a visit from the FBI shakes her foundations, and Irene once again learns just how little she knew about the man she loved. With help from their friends, Irene and her sons set up their lives while evidence mounts that the helicopter crash that killed Russ may not have been an accident.

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.

Gerri can't decide what's more devastating: learning her rock-solid marriage has big cracks, or the anger she feels as she tries to repair them. Always the anchor for friends and her children, she realizes it's time to look carefully at herself. The journey is more than revealing—it's transforming. Andy has come to believe that a lasting love is out of reach. When she finds herself attracted to a man without any of the qualities that usually appeal to her, she questions everything she thought she wanted in life.

Lark Smith has always had a plan for her life: find a fantastic guy, create a marriage as blissful as her parents’, pop out a couple of kids, and build a rewarding career as an oncologist. Things aren’t going so well. For one, the guy didn’t work out. Theoretically, she’d love to find someone else, but it hasn’t happened. Two, she’s just been transferred out of Oncology for being too emotional. (Is it her fault she’s a weeper?) Three, her parents just split up. Deviating from the plan was … well, not in the plan. A potential solution comes from the foul-tempered surgeon Lorenzo Santini.