Hopper is a twelve-year-old girl adjusting to a difficult family transition and a creepy new school. She initially attempts to make friends by faking an interest in basketball, hoping the sport might also draw the attention of her absent father. Her true passion emerges when she begins investigating the strange, robotic birds around campus and learning computer logic. She quickly proves herself to be an observant and determined problem-solver.

Eni is a seventh-grade student who has attended Stately Academy since kindergarten. Because his father is a software engineer, he possesses a foundational understanding of coding that proves invaluable for deciphering the school's secrets. He is highly perceptive, noticing the binary patterns in the campus birds long before anyone else pays attention.

Mr. Bee is the grouchy custodian at Stately Academy who holds the key to the school's strange technological phenomena. Though he appears to have no formal training, he is a skilled programmer who commands mechanical birds and automated machines to clean the campus and deter trespassers. He strictly protects his territory but recognizes potential in students who can solve his complex logic puzzles.

Josh is a student at Stately Academy who plays on the basketball team. He acts as a bully early in the school year, regularly mocking Hopper and questioning her presence. As the semester progresses, he grows insecure about losing his friendship with Eni and insists on following the others down into a secret underground portal.

Little Guy is a small robotic turtle programmed to carry out specific logic instructions. Functioning as a physical avatar for computer code, it follows both written scripts and verbal directions to turn on its leaf blower or walk in geometric patterns. The machine serves as an essential tool for the students as they practice their new skills.

Hopper's mother is a strict Mandarin teacher working at Stately Academy. She is currently preoccupied with adjusting to a new job, settling into a different town, and managing the aftermath of her recent marital separation. Her relationship with her daughter is deeply strained, as she enforces strict rules while struggling to communicate effectively.

Principal Dean is the head administrator of Stately Academy. He is dismissive of the student body and quick to hand out disciplinary punishments without listening to explanations. He appears to be involved in the broader mysteries of the campus, holding strange meetings that catch the attention of observant students.

Albert Gracie is Hopper's father, whose recent departure has left a significant void in her family. Though he is not physically present at the school, his love for basketball inspires his daughter to take up the sport. His name alone carries unexpected weight with certain staff members at Stately Academy.