This is the story of the rise to power of the largest wolf pack ever known, going from strength to strength they are now at a turning point in their lives. The balance of power is shifting within the pack, the leaders face a takeover challenge from within their own family. Winter in Yellowstone is six months of temperatures below freezing it can look beautiful but the conditions are fierce and this is a time when most animals struggle to survive, but it is also a time when one animal truly comes into it’s own, this is the time of the wolf and this BBC film follows the lives of such wolfs as the struggle for power begins.