Gwendy is a twelve-year-old girl struggling with her self-image and a hurtful nickname. Her life changes when a stranger entrusts her with a powerful, button-covered mahogany box. As she guards the magical item, she experiences sudden improvements in her health, appearance, and family life. She battles the heavy responsibility and isolation of keeping the box a secret from everyone she loves.

Frankie is a crude local teenager who actively targets Gwendy for her appearance. He is known around Castle Rock for his abrasive behavior and troubling reputation among his peers. As Gwendy grows older, his harassment takes on a more predatory tone, cementing him as a persistent source of fear in her life.

Mr. Farris is an observant man who selects Gwendy to be the custodian of the button box. He dresses in a dark suit and hat, presenting himself as a polite but enigmatic figure. He explains the basic functions of the levers and buttons but leaves the box's true scope shrouded in mystery.

Olive is Gwendy's childhood best friend. The two girls share a close bond built on innocent activities like riding bikes and hanging out in Olive's room. As Gwendy gains new popularity, Olive struggles with her own insecurities and a difficult home life, causing a painful rift between the girls.

Harry is a tall, handsome new arrival in Castle Rock who takes an immediate interest in Gwendy. He enjoys photography and quickly becomes a significant part of Gwendy's high school experience. His genuine affection offers Gwendy a sense of normalcy completely separate from magical influences.

Gwendy's father. Early in Gwendy's life, he and his wife struggle with their relationship and alcohol use. He later finds sudden domestic peace and adopts healthier habits, supporting his daughter as she matures.

Gwendy's mother. Her home life and daily habits improve significantly during Gwendy's middle school years. She cares deeply for her daughter but often attributes Gwendy's magical enhancements to normal teenage development.

Lenny is an older coin dealer who interacts with Gwendy when she decides to appraise her silver dollars. He is respectful and professional during their transaction. He proves to be protective when he steps in to ensure Gwendy's safety on the street.

Miss Chiles is Gwendy's middle school history teacher. She encourages her students to ask thoughtful questions about historical events, inadvertently prompting Gwendy to test the boundaries of her own secret power by asking about hypothetical buttons.

Jimmy is a local boy who associates with Frankie Stone. He acts as an accomplice during petty crimes and backs up Frankie during street altercations.

Sallie is one of Gwendy's high school friends. She represents the new, popular social circle Gwendy gains as she grows older. Their friendship is strained by Sallie's growing jealousy over Gwendy's seemingly effortless academic and athletic success.

Mr. Kepnes is Olive's father figure. His presence in the house creates a difficult domestic environment, compounding the social isolation Olive faces at school.