Seventeen-year-old Carrie struggles with a codeine addiction following an intensive jaw surgery pushed by her parents. Spending the summer of 1987 at her family's private island, Beechwood, she feels like an outsider compared to her conventionally beautiful sisters. She openly mourns the recent drowning of her youngest sister, Rosemary, which alienates her from the rest of the Sinclair family.

A charismatic teenage boy visiting the island, Pfeff quickly captures Carrie's attention and initiates a summer romance. Though he presents a carefree exterior, he exhibits a tendency to prioritize his own desires over the feelings of others. He openly admits to Carrie that he lacks academic ambition and relies on his family's wealth to secure his future.

Penny is Carrie's sixteen-year-old sister, whom Carrie considers the most beautiful and magnetic of the siblings. Penny prefers situations to remain peaceful, often avoiding difficult emotions or conflict. She closely follows their parents' expectation to maintain a perfect outward appearance despite internal pressures.

Tipper is the matriarch of the Sinclair family, known for hosting elaborate parties and maintaining a pristine household. She avoids discussing uncomfortable topics, preferring to keep herself busy rather than visibly mourn the loss of her youngest daughter. She keeps an old photograph of a former boyfriend hidden in her jewelry drawer.

Harris is the wealthy patriarch of the family who co-owns Beechwood Island. He insists that his family project strength at all times. His focus on outward perfection leads him to pressure Carrie into undergoing painful jaw surgery to correct what he perceives as a physical weakness.

Bess is Carrie's younger sister, characterized as a hardworking people-pleaser. She attends boarding school with her sisters and tries to follow her parents' directive to focus on the future rather than dwell on tragedy.

Rosemary is the youngest Sinclair sister who tragically drowned off the coast of Beechwood Island the previous summer. She returns as a ghost to visit Carrie at night, asking for fairy tales and companionship in her afterlife.

Yardley is Dean's daughter and Carrie's cousin. She balances a serious demeanor with a lighthearted sense of humor, acting as a grounding presence on the island. She brings her boyfriend, George, and his friends to Beechwood for the summer.

Johnny is Carrie's deceased eldest son. As a ghost, he visits his mother in the present day, prompting her to recount the difficult story of her youth to help him understand their family's history.

Dean is Harris's brother and part-owner of Beechwood Island. He arrives at the island unannounced, bringing along his children and their teenage friends for a summer vacation.

Tomkin is Dean's eleven-year-old son who spends the summer on Beechwood Island with his older sister and her friends.

George is Yardley's boyfriend who visits Beechwood Island for the summer. Carrie privately describes him as having a relatively plain personality.

Major is a teenage guest on the island who arrives suffering from seasickness. He spends his days boating with his friends and observing the Sinclair family dynamics.

Erin is a friend of Penny's who joins the Sinclair family on the island for the summer. She spends most of her time with Penny, offering a buffer from the family's tensions.

Buddy is a man from Tipper's past. Carrie discovers an old, scratched-out photograph of him hidden beneath the lining of her mother's jewelry drawer.