Eleanor Sunderland loves living on Nantucket in a gorgeous cliffside home that has been in her family for decades. Yet this year she can't help but feel a bit isolated, even as the island comes alive with summer tourists and travelers. Her best friend has skipped town on a last-minute cruise, leaving Eleanor lonely and feeling nostalgic about her family's weekend trips to the island, made less frequently in the years since her husband's passing. Now her money-driven children contact her mostly to complain and to beg her to sell her beloved home for a steep payout. Hoping to kick the season off on a good note, Eleanor decides that her seventieth birthday may be the perfect occasion for a much-needed reunion. Fresh from her college graduation, Eleanor's granddaughter, Ari, has just ended an engagement that felt less like true love and more like a chore. She longs for a change of scenery and to escape her parents' snobbish expectations. Taking advantage of her newfound freedom, Ari heads to Nantucket to clear her head before graduate school, moving in with her grandmother and taking a job at the local beach camp. As she watches Eleanor form a bond with an old acquaintance, Ari herself becomes smitten with a friend's charming older brother. But just as grandmother and granddaughter fall into a carefree routine, shocking discoveries throw them off course, and their ideas for the future seem suddenly uncertain.