Mark’s best friend since childhood, known as Jess or Jessie, who values loyalty and friendship, offering support and understanding to Mark while grappling with how best to help him.

Mark’s dog and loyal companion on his journey, known for his obedience and protective nature, serving as a constant source of love and friendship.

Mark’s mom and dad, unnamed in the narrative, who each respond differently to Mark’s illness and disappearance, but both exhibit care and resilience in supporting their son.

A six-year-old girl with curly red hair who talks with Mark on a bus ride, expanding his empathy and offering him a new perspective on handling emotions.

A biologist with the park service who gives Mark a ride, wearing a white cowboy hat and a green truck, and shares wisdom and support, becoming a friend to Mark during his journey.