At the western end of Loch Migdale, in the Scottish Highlands, sits a mysterious island. It could be a crannog; a man-made prehistoric island probably inhabited at some point in prehistory. On the shore nearby, there is an enigmatic circle cut into the ground. It might be a henge, or a cairn - no-one is sure - but it also seems to have been left by the prehistoric people who lived in this part of Scotland. The team work flat out in these beautiful surroundings, diving, hill walking and digging as they piece together the extraordinary story of Highland life 2,000 to 3,000 years ago.