Cameron is an athletic teenager from the rural town of Miles City, Montana. Following the sudden death of her parents, she lives with her grandmother and aunt while processing her grief. She is a competitive swimmer who spends her free time watching rented VHS tapes and building a makeshift dollhouse out of scavenged items. As she grows older, she begins to recognize and explore her attraction to other girls while questioning the strict religious rules imposed upon her.

Ruth is the born-again Christian sister of Cameron's late mother. She leaves her job as a flight attendant and sells her Florida condominium to raise Cameron in Miles City. She finds work as a sales representative for Sally-Q Tools, a company selling tool sets to women. Her rigid adherence to religious rules causes frequent conflict as she attempts to direct her niece's life.

Coley is an all-American girl from a prominent ranching family outside of Miles City. She attends church regularly and is nominated for Queen of the Bucking Horse Sale. She maintains a flawless public image that severely conflicts with her private desires, leading to deep internal shame about her actions.

Irene is Cameron's competitive childhood best friend who lives on a nearby ranch. After she and Cameron share their first kiss, the dynamic between them shifts uncomfortably. She eventually leaves Miles City to attend an expensive East Coast boarding school after her family gains sudden wealth from discovering dinosaur fossils on their property.

Lindsey is a confident teenager from Seattle who spends her summers in Montana with her father. She returns to Miles City one summer with short bleached hair and an eyebrow ring. She actively embraces her lesbian identity and makes it her mission to educate Cameron on queer culture by mailing her mixtapes, letters, and movies.

Rick is a handsome reverend in his thirties with shoulder-length brown hair and blue eyes. He runs God's Promise, a residential healing center for youth. He presents himself as an approachable and sympathetic figure who relates to the struggles of his students through his own past experiences.

Lydia is an older British woman who wears her silver hair in a tight ponytail. She serves as the psychologist, assistant director, and primary funder of God's Promise. She utilizes aggressive psychoanalytic exercises, such as the iceberg chart, to treat students, making her widely feared and unpopular among the teenagers.

Jane is a rebellious student at God's Promise who uses a prosthetic leg following a severe snowmobile accident. She grew up on an Idaho commune before her mother embraced religious fanaticism. She outright rejects the school's teachings and relies on her homesteading skills to cultivate and hide marijuana on the property.

Adam is an athletic teenager with glossy hair and long eyelashes who identifies as Two-Spirit, bridging two genders according to his Lakota heritage. While his mother views this as a sign of spiritual power, his father sends him to God's Promise for correction. He forms a close friendship with Cameron over their shared skepticism of the facility.

Mark is the son of a famous Nebraska minister. He is one of the most dedicated students at God's Promise, strictly following the rules and participating enthusiastically in phone fundraising. He faces intense internal pressure to please his father, participating in military-style pushups as a form of physical punishment during group therapy.

Grandma Post is Cameron's easy-going grandmother. Following the fatal car accident, she provides a comforting, quiet presence in the household, often acting as a buffer between Cameron and Ruth's strict religious rules. She keeps Cameron updated on family matters through letters.

Jamie is a wisecracking teenager and former junior high track star in Miles City. He works proudly at a local Taco John's restaurant. When he notices Cameron staring at Coley during a school dance, he confronts her and briefly attempts to date her to help address her confusion.

Margo is a semi-pro tennis player living in Germany who grew up with Cameron's mother. As a survivor of the historic Montana-Yellowstone earthquake, she visits Cameron to offer condolences and old family photographs. Cameron deeply admires her confident, gender-nonconforming presentation.

Erin is a student at God's Promise from Minnesota. She is a massive fan of the Minnesota Vikings and decorates her half of the room entirely in purple and yellow. She adheres strictly to the school's rules, suppressing her desires by following intense religious exercise videos and praying actively.

Brett is Coley Taylor's steady boyfriend. He is an avid soccer player who often leaves Miles City to attend prestigious athletic camps in California during the summer months, leaving Coley unsupervised.

Ray is a local deliveryman in Miles City. He begins dating Aunt Ruth and eventually becomes her fiancé, supporting her strict religious household rules and standing by her side during family interventions.

Mona is a college sophomore who works as a lifeguard. She is openly and casually queer, debating movie stars with Cameron and offering her a glimpse of same-sex attraction outside of a highly political context.

Pastor Crawford leads Gates of Praise, the conservative factory-like church that Ruth insists her family attend. He preaches strictly against homosexuality and intervenes directly in the lives of his congregants.

Bethany is a pretty teacher in her twenties at God's Promise. She oversees the self-paced education program for the students and provides Cameron with reading materials about the Montana-Yellowstone earthquake.

Ty is Coley Taylor's older brother. He helps secure alcohol for his sister's friends during the local festival and drunkenly interrupts a private evening at Coley's apartment, causing a panic.