In the picturesque Scottish Highlands, veterinarian Sir William "Billi" Sedgewick enjoys a serene life with his quirky but endearing friend, Gordon, a goat who behaves more like a dog. However, this idyllic existence is shattered by a stringent mandate from the Scottish government banning beavers and forcing their relocation to Norway. During one such operation, a transport truck filled with these furry creatures suffers a mishap, leading to some escaping into the wild. While most of the beavers are swiftly rounded up by the likes of the dedicated McKenzie and McTavish, one spirited little beaver named Bessie Boo manages to slip away, eventually finding refuge with a family of rabbits.
As time marches on, McKenzie transforms into a rather obsessive figure, embodying his role as a law enforcement officer in pursuit of his elusive prey. On the flip side, Bessie Boo flourishes within her new rabbit family, engaging in joyful tobogganing adventures. Yet, a moment of chaos strikes when a reckless incident sends her adopted brother, Wee Dave, and their mother tumbling into a treacherous river. Without a second thought, Bessie leaps into action to save them, and it is at this moment that Billi, Gordon, and young Jake become aware of the unfolding crisis thanks to an astute rabbit sighting.
Billi promptly gathers the community in the town square, but he soon becomes suspicious of McKenzie, whose true motives are cloaked in mystery. As Billi navigates the escalating situation regarding Bessie Boo, he not only finds and revives her mother but also spots Bessie and Wee Dave in a precarious position near Baron McToff's dam. Initially hesitant, Baron McToff eventually acquiesces to Billi’s compelling arguments, shutting down the turbines just in time for the group to rescue Wee Dave. However, joy turns to confusion as Bessie suddenly goes missing, leading to a frantic search.
In a bold attempt to recover Bessie, Gordon leaps off a cliff, hoping to intercept her, but ends up plunging into the river himself. The team rallies to rescue Gordon just as a submarine makes an unexpected appearance, causing mayhem. As apprehension grips the situation, Billi mobilizes a rescue effort involving a trampoline, showing his unwavering commitment to his friends. Miraculously, a quick-thinking pilot duck named Victoria throws a life-saving bottle of water to Billi, allowing him to revive Gordon and avert disaster. With Gordon safe on solid ground, they all breathe a sigh of relief, but the adventure is far from over.
As Lady Serena hands Bessie over to the oblivious submarine pilot, McKenzie seizes the chance to steal the precious beaver, kicking off a high-stakes chase that sees him commandeering Billi's trusty Land Rover. In retaliation, Billi pursues him in his sporty Aston Martin, leading to an outrageous skateboard chase throughout the undulating landscape of the Highlands. The tension peaks outside a fortified military installation where McKenzie’s plan to have Billi arrested backfires spectacularly when law enforcement arrives just in time. With consequences looming for McKenzie, Billi earns the opportunity to reunite Bessie with her rightful family, restoring order and justice.
As the commotion subsides, the townsfolk gather at the Catterness Inn to revel in their hard-fought victory, and a tearful Lady Serena is joyously reunited with her beloved Bessie. As the evening unfolds, Billi and his loyal companion, Toni Turner, quietly slip away into the enchanting moonlight, leaving behind a tapestry of excitement and valor in their wake.
