Nate Henn was full of humor, generosity and spirit. He was so alive. But then, in 2010, a series of terror-related bombings devastated Kampala, Uganda, leaving 74 people dead, including Henn. The news was a devastating blow for his best friend Tyler Dunning, who plunged into darkness, grief, anger and self-medication. His only solace? Exploring Rocky Mountain National Park, where the cliff faces, pine forests and wildlife softened his raw emotions. It was a failed attempt to climb Longs Peak that really changed him: The humbling experience sent him on a quest to visit all 59 U.S. national parks. From Glacier to Bryce, Saguaro to Kenai, the Everglades to Yellowstone, he roamed. And through the adventures that unfolded, he pieced his life back together. He started to let others in. And, finally, he was able to say goodbye.