A journey in the North America mountain chains to discover a unique animal: the mountain sheep. These big wild sheep are dark brown and have large curled horns and they have evolved to be able to survive in these inhospitable mountains. Two groups of sheep inhabit these mountains: the bighorns in the south and the thinhorns in the north. The film is about a journey to discover the secret of a unique form of sheep that has existed since the Ice Age and survived in one of the most difficult places on earth, a rocky and inaccessible habitat.