Harper is a resident of Martha's Vineyard who works delivering packages for Rooster Express. Separated from her identical twin sister for 14 years, she lives an unstructured, financially precarious life. She harbors deep grief over her estrangement from her family and seeks comfort in complicated romantic entanglements.

Tabitha is the structured identical twin of Harper, residing on Nantucket where she manages her mother's failing fashion boutique. She carries profound trauma from the death of her infant son 14 years ago, a tragedy that hardened her resentment toward her sister. Her controlled exterior masks deep emotional paralysis.

Ainsley is Tabitha's rebellious 16-year-old daughter. Growing up under her mother's distant parenting style, she acts out by throwing unauthorized parties and seeking validation from her peers. Despite her destructive choices, she possesses sharp emotional intelligence and craves genuine familial connection.

Eleanor is the formidable matriarch of the family and a renowned fashion designer on Nantucket. Her obsession with public image and control defines her interactions with her family, leading her to enforce strict boundaries. She uses her legacy, symbolized by the timeless Roxie dress, to exert influence over Tabitha.

Billy is a working-class electrician whose warmth and easygoing nature directly contrast with his ex-wife Eleanor's rigidity. He serves as Harper's primary anchor and steady ally. His relaxed attitude, however, borders on passivity regarding the 14-year feud between his daughters.

Reed is a respected physician on Martha's Vineyard who projects a thoughtful, consistent professional demeanor. Behind closed doors, he is deeply dissatisfied with his marriage and seeks comfort outside of it. His inability to make decisive choices creates significant complications for those connected to him.

Franklin is a well-liked local musician and carpenter who undertakes the renovation of Billy's house. Having experienced the tragic loss of his high school girlfriend, he possesses a deep well of empathy and understands the lingering effects of grief. He is fiercely loyal to his family.

Ramsay is Tabitha's recent ex-boyfriend, a prominent figure in the Nantucket insurance business. He embodies the socially approved, stable lifestyle that Eleanor desires for her daughter. Despite his polished exterior, he struggles to grasp the depth of Tabitha's emotional trauma.

Caylee is a charismatic young woman who initially appears as Ramsay's rebound girlfriend. She quickly proves herself to be resourceful and compassionate, taking a job at the failing family boutique. She offers much-needed progressive ideas for the business and provides gentle, non-judgmental guidance.

Drew is a young police sergeant on Martha's Vineyard. He maintains a casual relationship with Harper but prioritizes his standing in the community and the dignity of his badge. He operates primarily on social calculus, wishing to avoid public scandal.

Brendan is a former surfer living with a severe brain injury sustained in the water. He exists on the periphery of the island's social scene, providing Harper with quiet, unconditional companionship away from judgment.

Sadie is Reed's wife, a woman pushed to her emotional limits by the deterioration of her marriage. Following a public confrontation, she becomes intensely sensitive to community gossip and views any association with the Frost family as a personal betrayal.

Emma is Ainsley's cynical and manipulative peer at Nantucket High School. Enabled by a neglectful father, she encourages destructive behavior and readily deflects blame onto others to protect herself.

Candace is Ainsley's childhood best friend whose shifting allegiances create friction in their social circle. Her desire to maintain social status leads her to align with toxic peers, though she possesses a fundamental sense of right and wrong.

Meghan is the heavily pregnant manager of Eleanor's fashion boutique on Nantucket. She provides blunt, honest assessments about the store's failing, stuffy reputation and readily adapts to changes in the workplace.

Teddy is Ainsley's high school boyfriend who works at a local boutique hotel. He prioritizes his own well-being and attempts to distance himself from Ainsley when he perceives her behavior as a negative influence.

Edie is Brendan's devoted mother, living with him in a cottage on Chappaquiddick. She extends remarkable grace and support to Harper, offering her son's friend unconditional care during times of crisis.

Fish is Harper's loyal Siberian husky. He serves as a constant, non-judgmental companion who grounds Harper and accompanies her as she navigates unfamiliar environments.