Marin is an 18-year-old college freshman experiencing profound grief and isolation. She recently changed her major from Literature to Undeclared and avoids contact with people from her past in San Francisco. Raised by her grandfather after her mother's early death, she processes her emotions in solitude while struggling to find a sense of belonging in a harsh new environment.

Gramps is Marin's maternal grandfather and sole living relative, who raises her in San Francisco. He maintains strict boundaries within their shared home, spending most of his time in the back rooms. He bakes cakes and gives long lectures from the living room loveseat, but his private nature and fragile health cause underlying tension.

Mabel is a college student in Los Angeles and Marin's closest friend from California. She travels to New York during a winter storm to visit Marin, breaking a four-month period of silence between them. She brings a vibrant energy and a desire to understand why Marin abruptly fled her home.

Ana is Mabel's mother, a Mexican artist who creates intricate collages. She provides a warm, maternal presence in her home, differing greatly from the quiet and structured environment Marin shares with her grandfather. She frequently includes Marin in family activities and takes a keen interest in her well-being.

Javier is Mabel's father. He maintains a welcoming and supportive household in California, readily offering practical help and emotional support to his daughter's friends. He operates as a steady, reliable anchor for his family.

Hannah is Marin's college roommate in New York. She leaves for winter break but attempts to keep Marin connected by leaving behind a book of essays and checking in on her. She provides practical items, like winter boots, to help Marin adapt to the harsh climate.

Claire is Marin's late mother, who died in an accident at Ocean Beach when Marin was a toddler. Although absent, she remains a significant figure in Marin's thoughts, and local surfers occasionally offer Marin gifts in her memory.

Jacob is Mabel's boyfriend at her college in Los Angeles. His relationship with Mabel represents the life she is building independently of Marin.

Tommy is the groundskeeper at Marin's college campus in New York. He monitors the grounds during the winter break and offers his heated campus housing to students during a severe snowstorm.

Jones is one of Gramps's friends who regularly attends poker games at his house. He and his family provided temporary care for Marin during her childhood when her grandfather required hospitalization.

Emily is a surfer at Ocean Beach who knew Marin's mother. She shares stories with Marin about the local surfing community's respect for her family following Claire's death.

Ben is a high school friend of Marin and Mabel in California. He hosts parties and spends time with them in the local park, representing the normal high school social life Marin leaves behind.

Carlos is Mabel's older brother. He lives away from his parents' home and is preparing to start a family of his own, leaving his childhood bedroom available.

Griselda is Carlos's wife and Mabel's sister-in-law. She is expecting a baby, bringing new generation dynamics to Mabel's family.

Agnes is Jones's wife. She helps look after a young Marin during a difficult period in the grandfather's life when he requires a hospital stay.

Samantha is Jones and Agnes's daughter. She works at a local salon in California and serves as a familiar link to the time Marin spent with her family.