Banner begins life as an orphaned gray squirrel after his biological mother's early death. Discovered by a farmer's son, the infant squirrel is placed with a resident farm cat. This cat adopts him as her own, attaching a small bell to his neck that becomes a permanent feature. Raised by a feline, Banner develops atypical squirrel behaviors: heightened courage, a tendency to confront threats directly instead of fleeing, and occasional identification with cat-like mannerisms.

A catastrophic barn fire disrupts his farm life. Trapped during the chaos, his adoptive mother compels Banner to flee alone into the nearby forest. This separation forces him to navigate survival in the unfamiliar wild without maternal guidance. His initial isolation ends when he rescues a younger squirrel, Clay, from a fox attack, earning Clay's trust and marking Banner's entry into the squirrel community. Clay's mother, Lori, initially distrusts Banner due to his unusual background but gradually accepts him after he protects her family from a farmer.

Banner demonstrates adaptability by learning forest survival skills, often aided by Sue, a female squirrel drawn to his innocence and distinctive past. Sue actively teaches him foraging, nest-building, and predator evasion. Their bond deepens into a lifelong partnership, culminating in marriage and offspring. Banner's relationships extend beyond squirrels; he befriends an owl who initially intended to prey on him. Banner's defiant resistance earns the owl's respect, leading to a profound sacrifice where the owl intercepts a hunter's bullet meant for Banner, an event triggering Banner's intense grief.

Conflict emerges through Akācho, a rival squirrel competing for Sue's affection. Akācho employs cunning and underhanded tactics against Banner, creating sustained tension. This rivalry resolves when Akācho abandons his pursuit of Sue, though his motivations remain unclear. Banner's leadership surfaces during group crises, such as orchestrating Clay's rescue from captivity and defending the community against predators like foxes, eagles, and human hunters. His hybrid upbringing proves advantageous, enabling strategies unfamiliar to wild-raised squirrels.

Compassion defines key actions: persistently aiding a grieving mother rabbit whose offspring died, including attempts to impersonate her lost child to ease her sorrow, and rescuing a chipmunk despite its prior deception. A significant emotional arc concludes when Banner reunites with his adoptive cat mother, reaffirming their bond despite separation. His story culminates in establishing a family with Sue, transitioning into an elder role within the squirrel community, and reflecting on a life bridging two worlds.