Darkness looms over the forest. Sirius, a meek, true-hearted kitten, and Drogo, his bold, wild-at-heart brother, can sense it. Despite dire warnings from their human friend, Dan, Sirius and Drogo set off on an epic quest to uncover the mystery behind this darkness. Along the way, they face furious foes and reunite with Drogo's former friend and mentor, Beatrix the rabbit. Beatrix reveals that two devious predators, the Wolf and the Mountain Lion, have joined forces to secure their tyrannical rule over the forest and its innocent creatures. To defeat them, Sirius and Drogo must seek the aid of long-lost family members, enlist timid animals into an army, and overcome their own hidden doubts and fears. As good and evil clash in a climactic battle, one question remains: will darkness or the heart of a panther prevail?