The wolves have returned. The grizzly bear population is at an all-time high. The mountain lions never left. It's the dawn of a new era - and Yellowstone will never be the same. The presence of these predators touches every corner of Yellowstone. But on this rugged battlefield many questions remain: what does it take to survive, protect your turf, and raise young - all while trying to stay at the top of the food chain?

It's among the last of its kind: a river, still wild. The Yellowstone flows from the world's first national park into the life of the west, moving as few rivers do. Undamed, untamed, it changes with the seasons in a journey from the peaks to the plains.