Every year, thousands of aspiring thru-hikers head out on the Appalachian Trail for the adventure of a lifetime. One out of five of them will succeed, hiking all 2,000-odd miles of the path in a single season. In 2019, Canadian hiker Kirby Morrill hoped to become one of them. But her trip that year didn't end on top of Katahdin. Instead, it ended in an incident that would shake the trail's tight-knit community.