Henry is a young boy who possesses an intense, singular obsession with chocolate. He consumes it for every meal and in every conceivable form, from chocolate cake to chocolate-bar sandwiches. His unusual diet causes him to develop strange brown spots across his skin, forcing him to flee from medical authorities who view him as a scientific curiosity. He relies on his quick thinking and imagination when his condition attracts unwanted attention on the streets.

Mac is a large, friendly truck driver who picks up Henry during the boy's flight from the hospital. He possesses a calm, competent demeanor and a strong moral compass. As a Black man, Mac understands what it means to be treated as different, and he shares his own life experiences to help his young passenger feel less isolated and afraid.

Mr. Cane is a kindly, elderly candy distributor who owns a massive warehouse. He bears a slight physical resemblance to Santa Claus and possesses a deep, personal understanding of the confectionary world. He shares a unique history with Henry that allows him to offer specific guidance regarding the boy's unusual ailment.

Dr. Fargo is the chief of children's medicine at City Hospital. He approaches medicine with clinical detachment, focusing intensely on the scientific novelty of his patients. His eccentric demeanor and eagerness to make medical history completely terrify the young boy he is supposed to be treating.

Nurse Farthing runs the school infirmary. She provides a steady, composed presence during sudden medical emergencies. Unlike other adults who panic at unexplainable events, she remains methodical and focuses on comforting her frightened patients with a reassuring touch.

Louie is an incompetent criminal who hijacks a diesel truck in search of valuable cargo. He directs the robbery and issues orders to his captives, but his criminal aspirations far exceed his actual planning and operational abilities.

Lefty is the second half of an inept hijacking duo. He takes the wheel of the stolen vehicle to drive it to a secluded hideout in the country. Like his partner, he is motivated by a desire for quick wealth but lacks the competence to execute a successful heist.

Mrs. Kimmelfarber is a math teacher at the local school. She is the first authority figure to notice the strange physical changes occurring on one of her students. Her initial academic annoyance quickly gives way to genuine alarm as she witnesses the unexplainable transformation firsthand.

Mr. Green is a kind and caring parent who prioritizes immediate happiness over long-term discipline. He cheerfully indulges extreme dietary habits within his household without setting healthy boundaries or recognizing the potential risks.

Mrs. Green maintains a loving home but struggles to enforce dietary limits. She actively facilitates singular obsessions by preparing specialized, dessert-heavy meals and ensuring the pantry remains fully stocked with specific treats.

Mark is a 10-year-old boy who lives in the city with his parents and siblings. He observes the extreme eating habits occurring at the family dining table and generally tolerates them without complaint.

Elizabeth is a 13-year-old girl who watches her younger sibling's extreme diet on a daily basis. She accepts these unusual habits as a normal, established part of their family dynamic.

Frankie is an older student who targets peers based on their physical differences. He embodies the social cruelty of the schoolyard, using mockery and physical intimidation to isolate and frighten those who stand out.

Mr. Pangalos is a teacher who assists a colleague in examining strange marks on a student's skin. He initially dismisses the spots as regular freckles despite noticing a distinct, unusual scent in the room.

Michael is a student who experiences his best friend's uncharacteristic irritability on a Friday morning. He serves as the first witness to the psychological disruption that precedes a major physical illness.