A 2000 year old Iron Age underground chamber - a fogou - takes the Time Team deep into the far west of Cornwall.

Using the maps of a Cornish antiquarian who ended his days in a local lunatic asylum, the latest high-tech survey equipment and Tony's newly acquired skill at dowsing, the Team have just three days to unlock the fogou's secrets. What was the chamber used for, is there another underground passage in the area and did an Iron Age Settlement exist on the site?