Thirteen-year-old Jack is an avid reader and journal writer who enters the Witness Security Program after his father is arrested. Taking on the new identity of Zach Granger, he relocates to the desert town of Elko, Nevada. He struggles with the isolation of living a fake life and feels acute anger over his family's rapid adjustment. Despite his resentment, he gradually forms connections, begins working for the school custodian, and finds an outlet for his frustration.

Sam is the older, muscular custodian at Elko Middle School. He possesses significant musical talent and speaks multiple languages, though he lives a spartan life in a single room at the Nevada Hotel. He quickly becomes a protective figure for Zach, offering the boy a job sweeping out an old building and teaching him to channel his tension using a punching bag beneath the school's stage.

Alonzo is a wealthy drug cartel boss operating out of South America and Mexico. He dresses entirely in black, sports a ponytail, and freely employs violence to maintain his criminal empire. When his cargo pilot is arrested, Alonzo aggressively hunts for the relocated family to prevent any testimony that could destroy his operation.

Catalin is a perceptive Basque girl with long black hair. She works at her parents' restaurant in the Nevada Hotel and shares a close bond with her grandfather, who runs a sheep camp in the Ruby Mountains. She extends kindness to Zach on his first day of school, though she correctly suspects he is hiding details about his past.

Neil is an ex-Navy fighter pilot who started an independent cargo airline that quickly fell into debt. To save his business, he began running drugs for a cartel, leading to his arrest by the DEA. He deeply loves his children, having previously quit his job to help Jack recover from two broken legs, and decides to turn informant to ensure their safety.

Patricia is a resilient woman who adopts the alias Mary Granger to protect her children. She is furious about her husband's illegal activities and distances herself from him. She focuses entirely on rebuilding her family's finances by opening a bookstore in their new town, cutting and dyeing her hair blonde as part of her disguise.

Joanne is Jack's older sister, an outgoing teenager who dreams of becoming an actress. She treats her transition into the alias Wanda Granger like a theatrical performance. She quickly makes friends, secures a waitressing job, and wins the lead role in the school's production of The Opera Ghost, masking her deep grief over her father's actions.

Peter is an eighth-grade student widely disliked by his peers for his aggressive behavior. Adopted at a young age by financially irresponsible parents who prioritize gambling over raising him, Peter is desperate to secure bus fare to leave Elko. He harbors a crush on Catalin and develops a bitter grudge against Zach.

Donald is a U.S. Marshal assigned to protect the Osborne family. He acts as one of their federal handlers, insisting the children call him "Uncle Don" to maintain their cover story as they move across the country.

Doris is a U.S. Marshal who partners with Donald to protect the Osborne family. Operating under the alias "Aunt Doris," she helps comfort the family as they adjust to their severely downgraded living conditions in Nevada.

Agent Pelton is an operative with the Federal Drug Enforcement Agency who arrests Neil Osborne. He leverages Neil's desire to protect his family into a deal that will expose the drug cartel.

June is Patricia's trusted friend and attorney. She urges Patricia to cooperate with the federal agents and agrees to serve as the family's secret point of contact once they are relocated.

Benjamin is a famous, well-dressed criminal defense attorney secretly on Alonzo Aznar's payroll. He attempts to manipulate the Osborne family into rejecting government protection so the cartel can maintain control over Neil.

Known as "The Watchman," El Sereno is Aznar's surveillance expert. He diligently monitors June Sanders's mail, looking for any clue that will lead the cartel to the relocated family.

Berry is a cartel henchman working for Alonzo Aznar. He physically assists the drug lord in his violent efforts to locate and eliminate the Osborne family.

Paul is a henchman directly employed by Alonzo Aznar. He travels with his boss to execute intimidation tactics and track down the federal informants.

Mrs. Pyle is the principal of Elko Middle School. She quickly grows suspicious of Zach when he cannot recall details about his supposed past in Portland, and she handles disciplinary actions when a fight breaks out in the hallway.

Darrell is a red-headed student at Elko Middle School who lives in a tiny house filled with hunting accessories. He claims Zach as a friend and explains the gossipy nature of the small town, warning him that everyone knows everyone's business.

Benat is Catalin's broad-chested Basque grandfather who emigrated from the "old country" in 1946. He runs a traditional sheep herding operation in the mountains, rarely leaving his camp. He is a warm patriarch who embraces his cultural heritage and welcomes Zach into his circle.

Commander IF (Imaginary Friend) is a tiny wooden astronaut carved by Neil for Jack when the boy was recovering from broken legs. Operating as an internal sounding board, the toy helps Jack navigate the intense isolation and emotional trials of entering the Witness Security Program.