Mother
One way of interpreting this story is as Biblical allegory. The story opens with an illustration of Billy from the back looking through a window to the woods across the way while the text informs readers of his mother’s dominant authoritarian rule. She was always telling him exactly he is allowed and now allowed to do. Billy’s mother is, symbolically, God.
The Forest of Sin
To keep Billy from wandering into woods, his mother has created a whole mythos around it, with the help of its reputation around town. It is not just the wood, it is “The Forest of Sin.” This symbolically situates the woods, Biblical allegorical terms, as the location of the Tree of the Knowledge of Good and Evil. And because the mythos only serves to pique Billy’s curiosity and stimulate his desire to explore, it becomes the location of the forbidden fruit.
Billy
His mother’s dominant control has created a sense of purity and innocence which is nevertheless tempted by the Forest of Sin. Therefore, Billy is symbolic union of both Adam and Eve. He is the innocence which will be lost by biting from forbidden fruit of the tree of knowledge.
The Devil
The story even introduces the character of the tempter who lures the innocent into the Forest of Sin. Since he introduced as the Devil, it may seems as though he is not really a symbol at all, but it is notable that he does not really exist. The text makes clear that it is Billy who identifies him as the Devil and, what’s more, he exists only as voice whispering in his ear. Even more importantly, this “Devil” only appears and begins whispering when Billy is bored. All these details combined together serve the underscore that the “Devil” is not a literal character, but a symbolic manifestation of the imagination and Billy’s identifying him as evil is coincident with his mother’s dismissal of imagination as “rubbish.”
The Forest Creatures
Billy rebels against his mother’s God-like authority, submits to the powers of his imagination in the form of a Devil whispering in his ear and enters the woods. There he finds a multitude of wonders, some of which are good and one of which is truly bad, but all of which are magical and unlike anything he’s experienced outside the woods. The forest creatures represent an alternative possibility in this Biblical allegory in which biting going against the word of God and exploring the Tree of the Knowledge of God and Evil results not in being cast from paradise, but in discovering paradise.
