Cal is an 18-year-old senior at Central High School in St. Paul, Minnesota. He recounts his story from a jail cell, explaining how his ordinary life of delivering groceries and playing football changed. He initially dismisses Gretchen's claims of abuse, but his empathy soon takes over. He begins planning dangerous interventions to free her from her father.

Gretchen is a quiet, socially isolated high school student derisively called "Gretch the Wretch" by her peers. Her drab clothing, large brown oxfords, and lack of makeup are strictly mandated by her controlling father. She lives in constant fear of "going crazy" like her sister Helga. Despite this, she asks Cal for help to escape her abusive household.

Otto works at the local post office and enforces a strict, isolated existence for his family. He uses strict religious rules to control what Gretchen wears and whom she speaks to, actively preventing her from interacting with boys. Behind his pious facade, he acts as a violent predator who terrorizes his daughters.

Horace is a World War I veteran who has driven the Grand-Mississippi streetcar line for the Twin Cities Rapid Transit Company for ten years. He works as a proud, stubborn man who keeps a daily log of his runs and resents the transition from streetcars to buses. He advises his family to stay out of other people's business, yet he quietly cares for his children and neighborhood animals.

Peggy is Cal's 12-year-old sister. She shares her brother's empathy. She sneaks food to a rescued rabbit and leaves sandwiches for an abused dog next door, mirroring Cal's desire to protect the vulnerable.

Lola is a popular high school cheerleader who dates Tom Bradford. She struggles with her parents' recent divorce and her mother's strict refusal to let her contact her father in Baltimore. Cal harbors a deep, secret infatuation with her.

Helga is Gretchen's older sister who currently resides in a psychiatric hospital in Fergus Falls. Gretchen explains that Helga attempted to expose their father's abuse to the authorities. After their mother covered for Otto, he forced Helga into an institution.

Steve is one of Cal's best friends. He walks with a limp after contracting polio in the sixth grade, which leaves him only able to play goalie in hockey. He carries guilt over the childhood death of his younger brother, a tragedy his parents blame him for.

Sandy has been close friends with Cal since third grade. She works in the school's front office and forges hall passes for her friends. As an adopted teenager, she constantly scans strangers for physical similarities in hopes of finding her biological parents.

Lurine is Cal and Peggy's mother. Her experiences surviving the Great Depression make her fiercely frugal. She serves unappetizing leftovers and worries about violating the rules of their apartment building.

Ruth is Otto's wife and the mother of Gretchen and Helga. She remains unresponsive to Gretchen's pleas for help and enables her husband's absolute control over the family.

Emil was Horace's brother who lived in a messy, rural cabin near Grand Marais. He passed away when Cal was 14. Cal frequently reflects on the four summers they spent together, relying on Emil's lessons about nature to solve his current problems.

Jerry is a core member of Cal's friend group. He initiates the study hall incident that lands Cal in detention and jokes about Cal's social life. He plans to join the Navy after high school.

Tom dates Lola. His father pressures him to focus on academics and medical school rather than his social life.

Riley is a police sergeant working in St. Paul. He attempts to investigate vague, anonymous tips regarding a father abusing his daughter. He cannot take action without specific names or formal witness cooperation.

Pastor Ostrum is an ex-basketball player who leads the congregation at the Gant family's church. He visits parishioners to check on their well-being but struggles to see past the traditional facades of abusive households.