In the frigid valleys of Japan’s Shiga Highlands, a troop of snow monkeys make their way and raise their families in a complex society of rank and privilege where each knows their place. Their leader is still new to the job and something of a solitary grouch. But one little monkey, innocently unaware of his own lowly social rank, reaches out to this lonely leader, forming a bond with him that manages over time to warm his less than sunny disposition. It is a rare and remarkable gesture that alters both their lives. Changing seasons bring new babies to care for, a profusion of insects and blossoms to eat, family disagreements to squabble over and tragedies to overcome. Mating season brings competition for females as the days grow shorter and colder in a rush toward winter. But with their now confident leader to guide them and their families to shelter and care for them, this troop of snow monkeys is ready to face the world.

The Sierra Nevada, a mountain range running about 400 miles along the eastern side of California and stretches into Nevada, is home to three national parks: Sequoia, Kings Canyon and Yosemite. This is a land of giants, whether speaking of trees soaring to nearly 300 feet, or massive stone monoliths far taller than any skyscraper. But the force that has given rise to the earth's largest living trees and carved out the iconic natural landmarks of the Sierras is water. The role that water has played in the creation and evolution of Yosemite Valley cannot be overstated - feeding its numerous wild rivers and countless waterfalls, and making life in this stone wilderness possible. The second force, crucial to the Giant sequoias' ability to reproduce, is fire. It is the delicate balance of these two elements, water and fire, that is vital to the continued existence of the wildlife and trees that inhabit the Sierras. Despite the recent heavy rains and snowfall, scientists are finding that water is scarcer and the threat of fire is more likely as the area continues to experience rising temperatures upsetting that important balance. Geologists, ecologists, researchers and adventurers investigate how the changing climate is affecting one of America's greatest wildernesses.