Sam is a 12-year-old boy who leaves his crowded New York apartment to pursue independence in the Catskill Mountains. He arrives with basic tools and $40, planning to locate his family's abandoned farmland. Highly determined, he studies library books about nature but quickly discovers that hands-on experience is necessary to catch food and stay warm.

Frightful is a peregrine falcon whom Sam trains to hunt small game. She learns quickly, catching sparrows and eventually larger prey to keep the camp fed. As she matures, she communicates her contentment by puffing her feathers and provides essential companionship during long periods of isolation.

Mr. Gribley is a former sailor who currently works on the docks in New York City. He supports a large family in a cramped apartment and permits his son to wander off, assuming the boy will return quickly.

Bando is a college English professor enjoying his summer vacation in the woods. Initially suspected of being a criminal by an overly cautious Sam, he quickly proves to be a harmless and enthusiastic outdoorsman. He crafts clay jars and willow whistles during his visits to the mountain.

Bill is an older resident living in a cabin near the highway. He feeds a tired traveler a hearty meal of fish and oatmeal before providing practical instruction on striking a spark and maintaining a flame.

Miss Turner works as a librarian in a town near the Catskills. She provides access to historical county maps and field guides about hawks. She also offers practical help by trimming her young patron's hair with office scissors.

The Baron is a local weasel living beneath a boulder near the hemlock tree. He acts boldly around humans, sometimes nipping at pant legs or chasing off unaware hikers. His seasonal fur changes serve as a natural calendar for the approaching winter.

Jessie Coon James is a young raccoon that accepts food and shelter inside the hollow tree. She proves highly useful by digging up freshwater mussels from the nearby stream to supplement the camp's diet.

Mrs. Fielder is a wiry older woman who harvests fruit on the abandoned farmland. Viewing any solitary child as a lost wanderer, she insists on marching him back toward civilization.

Matt Spell is a high school student who works after school for a New York newspaper. He ventures out of the city hoping to secure a permanent reporting job by tracking down rumors of a boy surviving on deer and nuts.

Tom Sidler is a local youth who mocks the appearance of someone wearing homemade animal skins. After questioning the authenticity of the outfit, he accepts an invitation to visit the woods and see the survival skills firsthand.

Jim Handy works as a fire warden in the Catskill Mountains. His investigations into unexplained smoke trails force the local wildlife and unauthorized campers into hiding.

Aaron is a visiting songwriter looking for musical inspiration in the woods. He listens to original melodies based on local bird calls and plans to bring a portable organ to play them.

Great-grandfather Gribley is an ancestor who attempted to clear a farm in the dense mountain forest. Though his agricultural efforts collapsed, he left his name carved into a large beech tree on the property.

Mrs. Gribley is a city-dwelling mother managing a household of eleven children. She initially allows her son to leave for the wilderness under the assumption he will give up and come back quickly.