Coastal erosion exposes skeletal remains, revealing the haunting past of Medieval floating prisons in Britain. Sri Lankan researchers discover a special type of spider on an isolated island that was previously thought to be endemic to another country that's 30 miles away. New evidence leads archaeologists to unravel the unsolved mystery of the lost Roanoke settlers. Thousands of dead seals with strange corkscrew wounds confound a two-decade long wildlife enigma on Canada's Sable Island.