Catrina, who prefers to be called Cat, is an adolescent girl adjusting to a difficult cross-country move. She cares deeply for her younger sister, Maya, but experiences heavy guilt over her resentful feelings about leaving her friends behind. Skeptical by nature, Cat initially rejects the town's gloomy atmosphere and the locals' belief in ghosts. She is highly protective and constantly worries about Maya's health.

Maya is Catrina's younger sister, an eight-year-old girl living with cystic fibrosis. Her parents relocate the family to Northern California in hopes that the salty air will aid her breathing. She is highly energetic and maintains a bright outlook on the world despite her physical fragility. She finds herself fascinated by the town's ghostly history and desperately wants to learn what happens after death.

Carlos is a boy around Catrina's age who lives in Bahía de la Luna. He is open-minded and deeply connected to his Mexican heritage, working to keep the town's traditions alive by offering ghost tours to visitors. He is knowledgeable about the local spirits and Day of the Dead customs, eagerly sharing his culture with the new arrivals despite Catrina's initial resistance.

Catrina and Maya's parents are attentive caretakers who uproot their lives to Bahía de la Luna to improve Maya's health. The father is optimistic about their modest new house and the coastal environment. The mother, who drifted from her Mexican heritage after a strained relationship with her own mother, focuses heavily on managing Maya's medical needs and daily treatments.

José is Carlos's deceased uncle who passed away when he was eight years old. Remembered fondly by his family in Bahía de la Luna, his spirit remains tied to the living world through their ofrendas and stories. He retains a cheerful demeanor and is unbothered by his ghostly state, viewing his continued existence with a youthful curiosity.

Seo Young is a student in Catrina and Carlos's class in Bahía de la Luna. She is a friendly, outgoing girl who helps explain the town's history and the traditions of the harvest festival to Catrina, offering her a sense of normalcy and companionship in an unfamiliar place.

Javier is Carlos's father and a long-time resident of Bahía de la Luna. He proudly embraces his Mexican heritage and eagerly shares the town's ghostly history and traditional foods, such as tamales, with his new neighbors.

Abuela is the deceased grandmother of Catrina and Maya. Although she passed away prior to the events of the story, her memory becomes a focal point for the family. Building an ofrenda in her honor serves as the catalyst for the family to begin repairing their broken connection to their Mexican heritage.