Bee is a fifteen-year-old student living in Seattle with her parents. Born with a severe heart defect that required numerous surgeries during her infancy, she is now a bright and academically gifted teenager. She loves her mother fiercely and views her family life as completely normal, remaining cheerfully oblivious to her parents' growing eccentricities. She requests a family trip to Antarctica as a reward for her perfect grades, setting the story in motion.

Bernadette is a former architect who moved to Seattle from Los Angeles twenty years ago. Following personal and professional disappointments, she has become increasingly isolated and refuses to leave her home, a decaying property named Straight Gate. She avoids the other mothers at her daughter's school, referring to them as "gnats," and delegates all mundane tasks to a virtual assistant. The impending trip to Antarctica fills her with severe anxiety.

Elgin is an engineer at Microsoft and the presenter of a highly viewed TED Talk on artificial intelligence. He spends most of his time at work, remaining physically and emotionally detached from the daily happenings at his daughter's school. He worries deeply about his wife's mental health, interpreting her eccentricities as signs of a serious medical crisis.

Audrey is a prominent parent at Galer Street School and a devout Christian. She lives directly down the hill from the Branches in Seattle. She strongly dislikes Bernadette's refusal to participate in the school community and becomes hyper-focused on forcing the Branches to remove the invasive blackberry brambles spreading into her yard.

Soo-Lin is a divorced mother of two students at Galer Street School and an employee at Microsoft. She belongs to a self-help group called Victims Against Victimhood and uses their jargon to analyze her life. Her daily routine shifts dramatically when she receives a promotion to work as an administrative assistant on Elgin's artificial intelligence project.

Paul is a professor of architecture at the University of Southern California. He previously collaborated with Bernadette during her time working in Los Angeles. He holds her early architectural projects in high regard and considers her disappearance from the field to be a tragic waste of her artistic calling.

Dr. Kurtz is a psychiatrist affiliated with Madrona Hill, a residential treatment center on Orcas Island. Elgin contacts her for professional advice regarding Bernadette. She approaches the situation with a clinical eye, evaluating the family's living conditions and medical history to determine the best course of action.

Manjula is Bernadette's virtual assistant, purportedly based in Delhi. She handles everything from making restaurant reservations to securing prescription medications and booking international travel. Bernadette shares extensive personal information with her, treating the assistant as a confidante.

Kyle is Audrey and Warren's son, attending Galer Street School. He experiences significant behavioral and academic struggles that his mother attempts to downplay or ignore.

Warren is Audrey's husband and Kyle's father. He supports his wife as she navigates community politics and property disputes in their Seattle neighborhood.

Kennedy is Bee's best friend. She attends a church youth group that Bee joins, an activity that completely baffles Bernadette.

Gwen is the Head of School at Galer Street. She attempts to manage the conflicting personalities of the parents while leading a stressful fundraising campaign for a new building.

Mr. Levy is an eighth-grade teacher at Galer Street School. He recognizes Bee's intelligence and encourages her academic pursuits.

Tom is a blackberry abatement specialist hired by Audrey Griffin. He warns her about the risks of using heavy machinery on the hillside during the rainy season.

Judy is a real estate agent based in Los Angeles who helped Bernadette and Elgin find the properties that would become Bernadette's most famous architectural works.

David is a contractor who worked closely with Bernadette during her time in Los Angeles. He enthusiastically embraced her unconventional methods of reusing salvaged materials.

Michael is a celebrated real-life architect who served as an early mentor to Bernadette. He recognized her intense focus on practical, tactile problem-solving in building design.

Nigel is a British television personality who became Bernadette's neighbor in Los Angeles. Their relationship quickly devolved into a bitter legal and personal dispute over property rights.

Ollie is a consultant hired to help Galer Street School rebrand and raise funds for a new building. He uses heavy corporate jargon to encourage parents to attract a wealthier clientele.