St Kilda is Britain's wildest place, yet hardly anyone knows about it. The only British World Heritage Site nominated for both its extraordinary history and its wildlife, places it right up there with Machu Picchu, the Great Barrier Reef and Angkor Wat in terms of world significance... and it's right here on our doorstep! So wild are the conditions on and around St Kilda, that even the National Trust don't really know what's there, so we decided to find out. Join wildlife enthusiast Kate Humble, historian Dan Snow and climber and biologist Steve Backshall as they set out to uncover some of the mysteries about St Kilda. They investigate the secrets of its unique wildlife, the geological and archaeological remains, the never before explored underwater cave system, the plane wrecks from the Second World War, the myths about the people who once lived there, why they abandoned the island in 1930 and the mysteries that still surround the island's life today.