Leslie Patten had seen grizzly bears, wolves, coyotes, deer, elk, and many other species in her years living next to Yellowstone National Park. Yet, like most visitors, she had never seen a mountain lion--the charismatic yet enigmatic predator also known as a cougar, panther, or puma. She had only detected their ethereal presence on the landscape, which left her pondering where they were and what they were up to. After five years, through her serendipitous...