Sam is a 13- or 14-year-old boy who ran away from his New York City home two years ago to live independently in the wilderness. He knows the natural world well, foraging for food and creating tools like a stone-and-wood water mill. He values his peaceful, uncomplicated lifestyle and actively resists the intrusion of modern conveniences like electricity.

Alice is Sam's younger sister who moved to the mountain a year ago. She is inventive and determined, building her own treehouse and a plumping mill for grinding flour. Unlike Sam, she is eager to harness the mountain's resources for modern comforts and enrolls in correspondence courses to learn about electricity. She possesses a bold, fearless streak that often leads her into spontaneous adventures.

Bando is an English professor who befriended Sam during the boy's first year in the wilderness. Captivated by the natural environment, he bought a nearby cabin where he spends his free time. He acts as an adult companion for Sam, though he maintains a practical connection to civilization by enjoying hotel beds and canned food.

Zella is Bando's wife and a practicing lawyer who visits their mountain cabin despite her preference for urban amenities. She tolerates the primitive living conditions for her husband's sake but consistently campaigns for upgrades like electricity and running water. She possesses a sharp, logical mind that proves useful when interpreting clues about animal behavior.

Miss Turner is the librarian in the nearby town of Delhi. She serves as a crucial link to the outside world for Sam and Alice, providing them with the books they need to learn about primitive masonry, engineering, and local wildlife populations.

Frightful is a peregrine falcon raised from infancy by Sam. As an imprinted bird of prey, she views humans as her own kind and serves as a highly trained hunting partner. She is attuned to Sam's moods and the surrounding environment, often alerting him to approaching strangers.

A man presenting himself as a conservation officer who arrives at the mountain camp. He asserts that endangered peregrine falcons can only be legally kept by licensed falconers, setting off a chain of events that disrupts Sam's peaceful life.

Mrs. Strawberry is a friendly farmer who lives near Sam's mountain. She is an active member of the local rural community, providing physical labor for wilderness projects and teaching her neighbors how to communicate with her farm animals.

Crystal is Alice's pet pig. Rather than being a hindrance during wilderness travel, the pig proves capable in the forest, using a strong sense of smell to dig up edible tubers and locate water sources.

Hanni is a local farmer's daughter who meets Alice at a country fair. She invites Alice to stay at her family's farm and takes charge of showing the traveling pig at a subsequent 4-H club event.

Jessie Coon James is Alice's pet raccoon. A mischievous animal that relies on its human owner for regular feeding and care around the wilderness camp.

Slats is Mrs. Strawberry's horse. He communicates through a specific physical language that requires patience and observation to understand.