High Country: Itís fall in the Sierra Mountains, and Anna Pigeon is slinging hash in Yosemite National Parkís historic Ahwahnee Hotel. Four young people, all seasonal park employees, have disappeared, and two weeks of work by crack search-and-rescue teams have failed to turn up a single clue; investigators are unsure as to whether the four went AWOL for reasons of their own - or died in the park. Needing an out-of-park ranger to work undercover, Anna is detailed to dining-room duty; but after a week of waiting tables, she knows the missing employees are only the first indications of a sickness threatening the park. Hard Truth:Just three days after her wedding to Sheriff Paul Davidson, Anna Pigeon moves from Mississippi to Colorado to assume her new post as district ranger at Rocky Mountain National Park, where three girls have disappeared during a religious retreat. Two of the children reappear a month later, clad only in filthy underwear and claiming to remember nothing of the intervening weeks. Winter Study: It is January, and Park Ranger Anna Pigeon is sent to Isle Royale in Lake Superior to learn about managing and understanding wolves, as her home base of Rocky Mountain National Park might soon have its own pack of the magnificent, much- maligned animals. Sheís lodging in the islandís bunkhouse with the famed wolf study team, along with two scientists from Homeland Security, who are assessing the study with an eye to opening the park in the winters - an act that would effectively bring an end to the fifty-year project - so that the area can be manned to secure the scrap of border with Canada.