The brochure promised a "moderate-to-difficult" six-mile hike on the Maine-New Hampshire branch of the Appalachian Trail, where nine-year- old Trisha McFarland was to spend Saturday with her older brother, Pete, and her recently divorced mother. When she wanders off to escape their constant bickering, then tries to catch up by attempting a shortcut through the woods, Trisha strays deeper into a wilderness full of peril and terror. Especially when night falls.