Cash is a 17-year-old from rural East Tennessee who struggles with low self-esteem following his mother's death from a drug overdose. He feels deeply connected to the natural world, specifically the Pigeon River, which serves as a stabilizing presence in his life. Hesitant to leave his loving grandparents, he reluctantly accepts a scholarship to a prestigious Connecticut prep school alongside his best friend.

Delaney is a highly intelligent, inquisitive science prodigy from Sawyer. Dealing with the neglect of a mother with a substance use disorder, she is driven, focused, and eager to escape her economically depressed town. Her discovery of a new penicillin-like mold thrusts her into the national spotlight and earns her a scholarship to Middleford Academy.

Phillip, affectionately known as Papaw, is Cash's ailing grandfather. A man of deep moral conviction and unflappable principles, he faces isolation from his local church for defending LGBTQ+ culture and speaking out against racism. He provides unconditional love to Cash and teaches his grandson to view the natural world with wonder.

Dr. Atkins is a passionate English teacher and published poet at Middleford Academy. Hailing from Nashville, she provides a crucial link to Tennessee for Cash. She is highly unconventional, sporting blue-streaked hair, a nose ring, and tattoos, and she actively encourages her students to use poetry as an emotional outlet.

Viviani, often called Vi, is a vivacious student from Brazil who dreams of designing non-competitive video games. She loves the ocean and easily makes friends at the academy. Her charm and warmth make her a central part of Cash and Delaney's social circle, though she gently deflects Cash's romantic interest.

Alex is a driven, ambitious student of Korean descent from Austin, Texas. Planning to attend Yale Law and eventually run for Congress, he exudes confidence and purpose. He quickly forms a tight bond with Cash on the rowing team, offering camaraderie and steady support.

Tripp is Cash's wealthy, lacrosse-playing roommate from Arizona. He frequently mocks Cash's Appalachian background and family, embodying the elitism of Middleford Academy. His antagonistic and prejudiced behavior creates immediate tension in the dormitory.

Cash's grandmother manages a local pizza delivery business in Sawyer. She has helped raise Cash since he was a child, providing stability and practical care. Loving and resilient, she encourages Cash to seize the opportunity to attend Middleford and leave their economically depressed town.

Jason is the primary drug dealer in Sawyer, trafficking in a wide variety of narcotics. He views the depressed local economy as a business opportunity and attempts to hire Delaney to manufacture methamphetamines. He embodies the destructive forces ravaging the Appalachian community.

Desiree is Dr. Atkins's life partner and an award-winning chef. She provides a warm, welcoming, and hospitable environment for the students who cannot travel home for the holidays, offering them a lavish Thanksgiving meal.

Betsy is Cash's aunt, a pragmatic woman who understands the limitations of living in Sawyer. She provides crucial encouragement to Cash, warning him that making decisions based on fear will only lead to regret.

Cash's late mother struggled heavily with an opioid addiction. Her lifestyle was chaotic, characterized by casual neglect and a string of poorly chosen partners. Her accidental overdose remains the central trauma of Cash's adolescence.

Delaney's mother suffers from an ongoing substance use disorder. She is largely absent from Delaney's life, even leaving town with a new partner during the holidays. Her addiction serves as the primary catalyst for Delaney's drive to escape Sawyer.

Cash's father left the family to work on an oil rig in Louisiana and never returned. His absence contributes to Cash's feelings of abandonment and cements his reliance on his grandparents for parental support.