The National Trail System in the United States spans many thousands of miles of foot trail. The crown jewels of that system, of course, are the Appalachian National Scenic Trail, the Continental Divide Trail, and the Pacific Crest Trail.

While the adventurous might look at those long trails and set their sights on hiking one end from end, not all manage to complete the journey. Many become disillusioned after days spent hiking in the rain, or because they become homesick, or because of the blisters that sprout on their feet.

And some simply vanish.

In Sunday's podcast from the National Parks Traveler, we're joined by New York Times bestselling author Andrea Lankford to talk about her book, "Trail of the Lost, the Relentless Search to Bring home the Missing Hikers of the Pacific Crest Trail." It’s an incredible story Lankford has researched and woven together around three young men seemingly determined to go end to end on that trail.