Wavy is an eight-year-old girl growing up in a chaotic, abusive environment in the rural Midwest. Neglected by her parents, she assumes the role of protector for her younger brother and develops strict rules for survival, such as refusing to speak or be touched. She survives day-to-day by avoiding her mother's unpredictable rages and scavenging for food from the trash.

Kellen is a 24-year-old man with a violent past who works running drugs for Liam. Large and physically imposing, he feels marginalized by society but finds an unexpected sense of purpose in his interactions with Wavy. Having experienced severe abuse in his own childhood, he recognizes Wavy's vulnerability and assumes responsibility for her safety.

Val is Wavy's mother, struggling with severe drug addiction and mental health issues. Depending on her state, she can be completely bedridden or dangerously paranoid. She imposes strict, phobia-driven rules on her children about germs, forcing them to adopt bizarre survival behaviors to avoid her wrath.

Amy is Wavy's suburban cousin who finds Wavy's eccentricities fascinating rather than off-putting. She provides a stable, middle-class perspective on the chaos surrounding Wavy's life. Amy cherishes the secret bond she shares with her cousin and observes Wavy's growth with protective empathy.

Liam is Wavy's father, a violent and powerful meth dealer operating out of a rural compound. He is frequently absent from the family home but brings chaos, abuse, and illicit activity into Wavy's life whenever he returns. He commands fear from his employees and family alike.

Renee is an upper-middle-class college student who becomes Wavy's roommate. Initially superficial and prone to exaggerating tragedies for attention, Renee eventually learns to understand Wavy's deeply rooted real-world trauma. She transforms from a self-absorbed student into a dedicated ally.

Donal is Wavy's younger brother, born while their mother was incarcerated. Growing up in the same neglectful environment as his sister, he relies entirely on Wavy for his basic needs and protection from their parents' erratic behavior. He remains innocent of the full reality of their situation for a long time.

Brenda is Val's sister and Wavy's aunt. Living a comfortable middle-class suburban life, she is horrified by Val's choices and intermittently takes Wavy and Donal in. She is driven by a profound fear of poverty and a strong desire to maintain social appearances, which often overrides her empathy.

Grandma is Val and Brenda's mother, who provides Wavy with her first genuine experience of safety. Though her time with Wavy is limited by a cancer diagnosis, she recognizes Wavy's intelligence and shares her love of the night sky, leaving a permanent positive impact on her granddaughter.

Sean is Liam's brother, who shares the family's deep involvement in the drug world. He frequently asks Liam for loans and harbors deep resentments. His presence adds an extra layer of volatility and danger to the environment at the farmhouse.

Butch is one of Liam's loyal drug dealers and runners. While embedded in the criminal lifestyle, he possesses a degree of moral discomfort regarding the abuse Wavy suffers. However, he consistently prioritizes the safety of the meth operation over intervening on a child's behalf.

Dee is one of Liam's mistresses who frequents the meth compound. Living on the margins of society, she is dependent on Liam for her lifestyle and views Val with a mixture of pity and intense rivalry.

Sandy is another of Liam's girlfriends who spends significant time at the ranch. She attempts to bond with Wavy by teaching her about makeup and clothing, inadvertently encouraging the young girl's imitation of adult, sexualized behaviors.

Cutcheon is the owner of the motorcycle repair shop where Kellen works. Having experienced extreme poverty and a highly unconventional marriage in his own past, he offers Kellen rare understanding and serves as a surrogate father figure.

Lisa is Wavy's third-grade teacher. She recognizes Wavy's intellectual gifts but is quickly overwhelmed by her intense trauma responses and refusal to speak. She shows how institutional safety nets fail children in extreme poverty.

Bill is Brenda's husband and Amy's father. He resents the disruption and chaos that Wavy and Donal bring to his quiet suburban life, believing his tax dollars should handle the problems created by his wife's impoverished relatives.

Leslie is Amy's older sister and Wavy's cousin. She is highly focused on boys, appearances, and social norms, and she frequently acts impatient and dismissive regarding Wavy's strange behaviors.

Grant is a local sheriff familiar with Kellen's violent childhood. He is more patient and understanding of the local community's specific dynamics than the federal agents who arrive in town, often relying on his long-term knowledge of the residents.