When there’s a suspicious death in the backcountry, the National Park Service relies on 33 special agents of the Investigative Services Branch — basically the vacation FBI. They solve cases ranging from murder to theft of native artifacts. And crime scenes include more than 85 million acres of remote, federally protected land. Limited resources mean an agent generally handles each step of the investigation. That was the case after a woman tragically fell to her death during her 2012 wedding anniversary trip at Rocky Mountain National Park — and the distraught husband’s story didn’t add up.