Kelley is the patriarch of the Quinn family and owner of the Winter Street Inn on Nantucket. Having recently separated from his second wife, he is running the business by himself during the busy holiday season. He attempts to maintain a steady environment for his adult children and grandchildren, though he privately suffers from profound heartbreak and exhaustion.

Mitzi is Kelley's estranged second wife, having left him the previous year for the man who played the inn's Santa Claus. She is consumed by anxiety over her deployed son, relying heavily on alcohol to dull her emotional pain. Her spontaneous decision to return to Nantucket disrupts the delicate peace Kelley has established at the inn.

Ava is the middle child of Kelley and Margaret. She works as an elementary school music teacher on Nantucket and hopes to soon build a family of her own. Though she values predictability, her self-assurance wavers when she faces unexpected jealousy and the sudden reappearance of an old flame.

Margaret is Kelley's first wife and a highly successful CBS news anchor. She is a composed and wealthy matriarch who funds the inn to keep the family business afloat. She balances her demanding public career with her responsibilities as a mother and grandmother.

Jennifer is Patrick's wife, tasked with raising their three young boys alone while maintaining her professional career. Outwardly stoic, she wears a metaphorical suit of armor to project competence to the outside world. Privately, she masks her profound loneliness and stress by secretly consuming prescription painkillers.

Kevin is the youngest son of Kelley and Margaret. Having moved past previous life mistakes, he now successfully manages the day-to-day operations of the Winter Street Inn. He is wholly devoted to his girlfriend and their newborn daughter, though he remains fearful that his toxic past might ruin his current happiness.

Patrick is the eldest son of Kelley and Margaret. He is currently serving time in prison for an insider-trading scandal. Though he is not physically present at the inn, his mistakes actively burden his wife and children.

Bart is the only child of Kelley and Mitzi. He is a young Marine currently deployed in Afghanistan, whose platoon was recently taken by an extremist faction. His uncertain fate casts a dark cloud over the entire Christmas Stroll weekend.

Isabelle is the cook at the Winter Street Inn and Kevin's partner. As a new mother, she experiences severe anxiety whenever she is separated from her baby. She remains acutely insecure about Kevin's history with his ex-wife.

George is the man who played Santa Claus at the Winter Street Inn and maintained a long-running affair with Mitzi. He now lives with her, though he struggles to support her through the trauma of her missing son.

Drake is a pediatric brain surgeon from Sloan Kettering who is dating Margaret. He travels to Nantucket for the holiday weekend, offering a steadying, outside presence to the frantic Quinn household.

Scott is the principal at Nantucket Elementary School and Ava's boyfriend. He is generally viewed as a reliable and decent man, though his excessive attention to a female coworker creates a rift in his relationship.

Nathaniel is Ava's ex-boyfriend who suddenly reappears on Nantucket during the holiday weekend. He is persistent in his efforts to win her back, intentionally disrupting her current relationship.

Norah is Kevin's ex-wife, a woman who previously derailed his life and has now moved back to Nantucket to live with her mother. She actively attempts to provoke Kevin and takes pleasure in discovering the secret flaws of the Quinn family.

Roxanne is an English teacher at the local high school. She openly flirts with Scott and, after suffering an injury, pulls his attention entirely away from the Quinn family events.

Barrett is the eleven-year-old eldest son of Patrick and Jennifer. Deeply affected by his father's imprisonment, he channels his confusion and pain into aggressive, defiant behavior aimed at his mother.

Genevieve is the newborn daughter of Kevin and Isabelle. Her upcoming christening serves as the central event that forces the extended Quinn family to gather in one place.

Mary Rose is a kind woman who meets George during the holiday festivities. She provides him with a brief escape from the emotional heaviness of his relationship with Mitzi.

Darcy is Margaret's professional assistant. She works behind the scenes to gather and relay critical, classified information regarding Bart's military unit.