Petey is a man born with severe cerebral palsy who spends his life residing in state institutions and nursing homes. Due to the severe presentation of his condition, his body involuntarily contorts, he requires constant physical care, and he can only speak a few words at a time. Misdiagnosed as an infant with an intellectual disability, Petey is placed in a psychiatric facility where his sharp, engaged mind is hidden behind his physical limitations. He remains exceptionally observant, patient, and eager to connect with others despite the neglect he experiences.

Trevor is an eighth-grade student living in Bozeman, Montana. Frustrated by his parents' frequent moves, he initially refuses to make new friends to avoid the pain of inevitably saying goodbye. He is highly principled and instinctively protective, traits that push him to defend Petey and ultimately take on the role of his fiercest advocate. He dedicates himself to improving Petey's quality of life by fundraising for a customized wheelchair.

Calvin is a young boy diagnosed with mild intellectual disabilities and clubfeet, requiring him to use a wheelchair. He is energetic, highly vocal, and naturally extroverted, often causing a commotion on the ward. He quickly attaches himself to Petey, figuring out how to translate Petey's subtle vocalizations and acting as his link to the rest of the patients and staff.

Owen is a 65-year-old former cattle rancher who takes a demanding job as a hospital attendant because he wants to help people. He is shocked by the poor conditions on the ward and immediately questions the dismissive attitudes of his coworkers. Recognizing the genuine connection and intelligence shared by Petey and Calvin, he bends hospital rules to improve their daily lives.

Sarah is Petey's mother. She spends the first two years of his life trying to provide the intense care he requires, hoping to see developmental improvements. Eventually, acting on the recommendation of specialists who claim her son is an "idiot," she makes the painful choice to surrender him to state custody.

Roy is Petey's father. He stands by his wife as they follow the medical advice of the era, surrendering their severely disabled toddler to an institution under the belief that they can no longer properly care for him at home.

Esteban is a 17-year-old former migrant worker who seeks employment at the hospital specifically to help people. Assigned to the Infants' Ward, he is the first person to realize that Petey is capable of intentional communication. He shares his chocolate with Petey and defends the patients from being called freaks by visitors.

Joe is a former railroad worker who took a job at the hospital after a progressive muscular disease made physical labor impossible. He develops a fond attachment to Petey and Calvin, actively disputing the doctor's claims that Petey is unintelligent. He provides the boys with their first Christmas presents, validating their humanity.

Cassie is an elegant and kind young woman who takes a nursing job after her husband is drafted. She is one of the few staff members who is Petey's age, and she treats him with profound respect and gentleness. She takes the time to learn his speech patterns, brings her baby to visit him, and affirms his worth as a person.

Sissy is a nurse at the Bozeman Nursing Home who provides competent and respectful care. Aware of Petey's correct diagnosis of cerebral palsy, she knows he is fully cognitive. She actively recruits Trevor to come visit Petey, recognizing that the lonely teenager and the isolated older man might help each other.

Kenny is a middle school bully who targets vulnerable people. He repeatedly threatens Trevor at school for defending the nursing home patient, escalating his intimidation until Trevor confronts him directly.

Mr. Hedrick is the administrator of the Bozeman Nursing Home. He is practical to the point of coldness, citing Petey's age and physical limitations as reasons to deny funding for a functional wheelchair. He dismisses Trevor's concerns with a condescending attitude.

Shawna is a local teenager who initially stares at Petey out of shock, prompting an angry response from Trevor. After Trevor apologizes, she expresses genuine curiosity and a willingness to learn. She quickly becomes a steady friend, joining Trevor and Petey on their walks and outings.

Boyd is a volunteer who works closely with Calvin at a group home in Hamilton. He drives Calvin to Bozeman and assists Trevor with the logistics of managing both Petey and Calvin during their outdoor excursions.

Georgia is a physical therapist who is moved by Trevor's determination. She agrees to provide the mandatory evaluation for Petey's new wheelchair at no cost, provided Trevor can raise the necessary funds for the equipment.

Ann is a local newspaper reporter who meets Petey and is immediately charmed by him. She writes an article to raise awareness about Trevor's wheelchair fund, believing that Petey's history of institutionalization will resonate with the public.

Gus is a portly ward attendant at the state hospital who exhibits a profound lack of patience and respect for the patients. He carelessly dismisses Petey's smiles and vocalizations as mere conditioning rather than signs of intelligence.

Mrs. Elgin is the nursing director at Warm Springs. While she recognizes Owen's ambition, she strictly enforces the hospital's rigid protocols, instructing him not to question the psychiatrists' outdated and incorrect assessments of the patients.