For centuries, the Northwest Passage was the Holy Grail of naval exploration. A clear waterway between Canada and the Arctic Circle would (theoretically) cut down on travel time between hemispheres, but it proved incredibly elusive. Although European sailors first began seeking the much-rumored route since the 1490s, the first successful navigation of the Northwest Passage wouldn't come until the 20th century, and even then, it took three full years to get from one ocean to the other. Sir Francis Drake, Captain James Cook, and Henry Hudson (of Hudson Bay fame) would all attempt the journey, and all would meet with failure.
The most disastrous attempt, however, was the Franklin Expedition, which cost the lives of all 129 crew members. How they died has always been something of a mystery — but a modern-day dentist believes he's finally solved the riddle.