NOVA presents an exclusive breakthrough in the greatest unsolved mystery in Arctic exploration. In 1845, British explorer Sir John Franklin set off to chart the elusive Northwest Passage, commanding 128 men in two robust and well-stocked Royal Navy ships, the Erebus and Terror. They were never heard from again. Eventually, searchers found tantalising clues to their fate: a hastily written note left on an island, exhumed bodies suggesting lead poisoning, discarded human bones with marks of cannibalism and Inuit legends of ghost ships. But no trace of the ships was ever found.