Joel is a boy preparing to enter junior high school. He is scrupulous, conscientious, and prone to worrying about potential dangers in his environment. He values harmony and looks up to the authority figures in his life, particularly his father. Despite his naturally cautious personality, he frequently yields to the wilder, riskier ideas proposed by his best friend.

Tony is a confident, talkative, and adventurous boy who has been best friends with Joel since infancy. He enjoys taking risks and often devises schemes to make money, such as selling mashed worms as bait or flattened pennies. Underneath his reckless exterior, he harbors secret fears and insecurities, specifically regarding his physical abilities and the upcoming transition to junior high.

Mr. Bates is Joel's loving but firm father. He is protective of his sons and frequently warns them about potential hazards, like cars on the road. He maintains high standards for behavior and emphasizes the importance of integrity, asking his son to swear on his honor to keep his promises.

Mrs. Zabrinsky is Tony's mother and a long-time caretaker for the children in the neighborhood. She has a deep history with the Bates family, having watched over them for years. She cares deeply for her son and quietly guards the truth about his personal fears.

Mr. Zabrinsky is Tony's father. Unlike the gentle Mr. Bates, he has a temperamental nature and uses physical discipline, such as a belt, to punish his children. His harsh parenting style causes underlying anxiety in his household.

Mrs. Bates is Joel and Bobby's mother. She expects open communication from her children and quickly notices when their routines or behaviors seem unusual.

Bobby is Joel's four-year-old younger brother. He is energetic and eager to tag along with older children, though his older brother often views him as a childish nuisance. He is highly observant and requires careful supervision from his family.