**Box is in place as of July 2014**
This letterbox is (loosely) based on the novella "At the Mountains of Madness" by HP Lovecraft. You don't need to have read the book or even have a copy of the book to find this letterbox but it might make it more enjoyable (depending on how tiresome you find reading Lovecraft's stories!). This letterbox imagines what has happened in the years following the events in the book.
The clues are in .pdf format here. There are two long-winded pages!
Good luck, have fun, enjoy the mountains (and the fabled Plateau of Leng?)...