The Yeti - a mysterious creature that walks on two legs - has been part of Tibetan folklore for thousands of years. Scientist Mark Evans has long been intrigued by the legend, and has assembled a team of leading international geneticists who will use cutting-edge DNA analysis to help him find out, once and for all, if there's a rational explanation for the 'Abominable Snowman'. He travels halfway around the world on a mission to explore two competing theories for the Yeti. Is it a different species of human that was pushed to the margins by Homo sapiens and clung on in the high Himalaya until more recently than anyone thought possible? Or is the Yeti an unknown bear species? Mark meets renowned mountaineer Reinhold Messner who claims to have encountered a Yeti and is convinced that it's some kind of special bear. British mountaineer Steve Berry shows Mark intriguing photos of footprints on an unexplored Himalayan mountain.