Langtang National Park is one of Nepal's most inviting tourist attractions. With breathtaking mountain views and clear, glassy lakes, the park spawns 660 square miles and is home to some of the country's most spectacular wildlife, including snow leopards and red pandas. While the park attracts up to 18,000 visitors a year, it is no stranger to losing some of those travellers. Aubrey Sacco is one of those who vanished within its boundaries, never to be seen again.