Historian Dan Snow, naturalist Steve Backshall and wildlife enthusiast Kate Humble set out to solve some of the mysteries of St Kilda in Scotland's Outer Hebrides - the only British World Heritage Site nominated for both its extraordinary history and its wildlife. Inhabited just 80 years ago, St Kilda is now home to seabirds and seals but these islands remain a place of mystery. When the St Kildans suddenly abandoned their homes, they left behind a place full of secrets and Dan, Steve and Kate travel to these far flung islands to find out just who were the strange and remarkable people, why did they leave, and can St Kilda's amazing wildlife survive in the modern world?