The magic tree house whisks siblings Jack and Annie back to 1903 California, landing them in the crown of a giant sequoia in Yosemite National Park. Tasked by Morgan le Fay to “save the wilderness,” the pair must use sketchbooks to document the nature around them. During their mission, they join a historic camping trip with naturalist John Muir and President Theodore Roosevelt. Along the way, they face the dangers of the wild, including a heart-pounding encounter with a grizzly bear, and learn that protecting nature requires feeling its value with the heart, not just seeing it with the eyes.