The Time Team travel to the site of a Dark Age man-made island - known as a crannog - in Llangorse lake, near Brecon in Wales. The archaeologists have just three days to unravel some of the questions raised by a member of the public about the lake where, over 1,000 years ago, a Welsh king built an island base. The site poses a number of questions: what happened to the people who lived there? What was their connection with Ireland and the ancient script known as ogham, previously found on nearby stones?