Freckles is an adult orphan, just under twenty years of age, with bright red hair and a freckled complexion. His left hand is missing at the wrist. After he leaves the orphanage he applies for a job with the Grand Rapids lumber company, guarding timber in the Limberlost Swamp. The lumber company manager is impressed by the boy's polite assertiveness and hires him despite his youth and disability. He gives his name only as "Freckles", insisting that he has no name of his own.
Freckles' duty is to twice a day walk the perimeter of the lumber company's land, a seven mile trek through lonely swampland, and to be on the watch for those who aim to steal the expensive timber. Freckles' weapons are limited to a revolver and a stout stick, which he carries at all times and uses to test to wire that marks the company's boundaries. At night Freckles boards with Duncan, head teamster for the lumber company, and Duncan's wife, who becomes a mother figure to Freckles.
Initially terrified of the wilderness after a lifetime in an urban environment, Freckles first conquers his fears and then develops an interest in the wildlife of the swamp. He begins working on preserving the wildlife of the swamp while going about his duty of protecting it.