Samuel is an ophthalmologist who frequently reflects on his 1950s childhood. He was born with ocular albinism, a rare genetic condition causing his irises to appear red. Raised in a devout Catholic household, he struggles with his mother's insistence that his physical difference is a blessing from God. At school, he faces severe ostracization and relies heavily on his small circle of fiercely loyal friends for protection and support.

Madeline is Samuel's deeply religious and protective mother. She views her son's red eyes as a miraculous sign of God's will rather than a disability. A strong-willed woman, she meticulously documents Samuel's milestones in photo albums and refuses to let him hide from the world. She aggressively advocates for his inclusion at the local Catholic school, placing her at odds with conservative administrators.

Ernie is the only Black student at Our Lady of Mercy Catholic School and Samuel's closest childhood companion. Originally from Detroit, he bonds with Samuel over their shared status as outsiders. He is a gifted athlete with a quick wit, providing a much-needed defense against schoolyard cruelty. In the 1989 timeline, he runs a successful family technology business and remains deeply connected to Samuel.

David is a relentless schoolyard bully who torments Samuel and Ernie. Coming from a harsh home environment, he takes out his anger on those he perceives as weak, utilizing both physical violence and cruel insults. In the 1989 timeline, he is an imposing police officer whose intimidating presence continues to cast a dark shadow over his own family and Samuel's life.

Michaela is a fiercely independent girl sent to Our Lady of Mercy for behavioral issues. She challenges traditional gender expectations through her athletic abilities and outright refusal to be intimidated by male students. In adulthood, she works as an ophthalmologist and co-owns a medical practice with Samuel. She serves as his brutally honest confidante and fiercely protects him from poor personal decisions.

Max is Samuel's father, a hardworking and practical pharmacist. He is less driven by religious fervor than his wife and worries constantly about shielding his son from the cruelty of the world. He prefers to avoid conflict but demonstrates his love through quiet, steadfast support and gifts like a blue Ford Falcon.

Eva is Samuel's romantic partner in the 1989 timeline. She works as a flight attendant and maintains a busy travel schedule. She is adamant about not having children and pushes Samuel toward sterilization, which creates an emotional distance in their relationship.

Sister Beatrice is the austere principal of Our Lady of Mercy Catholic School. She views Samuel's differences with suspicion, refers to him as 'Devil Boy,' and attempts to exclude him from the student body. She rules the school with a heavy, authoritarian hand and often targets vulnerable students with harsh punishments.

Father Brogan is a priest at Our Lady of Mercy who intervenes on Samuel's behalf during conflicts with administrators and students. Unlike Sister Beatrice, he demonstrates genuine compassion and a strong sense of justice. He steps in to protect students from severe bullying and holds offenders accountable.

Trina is the ex-wife of David Bateman. She brings her daughter to Samuel's ophthalmology clinic for a severe eye injury. She claims the injury resulted from a bicycle accident, acting out of fear of her ex-husband's volatile temper and history of domestic abuse.

Donna is a public high school senior who works part-time at the Hill family pharmacy. She initiates a physical relationship with Samuel, appearing entirely unaffected by his eye color.

Daniela is the young daughter of Trina Crouch and David Bateman. She suffers a severe eye injury that requires Samuel's medical intervention. Her arrival at the eye clinic prompts a tense intersection between Samuel's past trauma and his present medical profession.

Sister Kathleen is a relatively fair-minded nun who teaches first grade at Our Lady of Mercy. She attempts to defend Samuel against Sister Beatrice's immediate assumptions. Her classroom provides a slightly more supportive environment for Samuel and Ernie during their early school years.

Dan is a local news reporter and an old college friend of Madeline Hill. He uses his journalistic influence and media access to pressure the Catholic school into officially admitting Samuel.

Tommy is one of David Bateman's childhood cronies. He initially participates in harassing Samuel but shows hesitation and asks David to stop when the physical violence escalates too far.

Dr. Pridemore is a medical specialist at Stanford University who formally diagnoses Samuel's ocular albinism. He remains a professional contact and lifelong friend to the Hill family as Samuel grows up.

Michelle is Ernie Cantwell's wife in the 1989 timeline. She lives a quiet life with him and their two sons, welcoming Samuel into their home during emergencies.