Denali : Documentary on the Dangerous and Deadly Mount McKinley. In a time when there were few unmapped regions left on Earth, some of the last places for humans to set foot were the tops of the tallest mountains. Teams from several nations competed to be first. After many tried and died, by the middle of the 20th century, the most famous peak, Everest, was conquered. But on the other side of the world, in Alaska, close to the Arctic Circle, there is a mountain as challenging to climb as Everest. For on its slopes lurks an invisible killer.