Kholat Syakhl is in one of the most desolate mountain ranges in the world. In Russian, it's called "Dead Peak". Not far from the Arctic Circle, it's a lonely, windswept crag - which makes it a beacon for daring backcountry hikers who want the ultimate challenge.
And so, in 1959, a small group of Soviet hikers led by Igor Dyatlov set out with fanfare on a never-attempted hike across the brutal landscape.
They never reached their destination.
Two weeks after the hikers went missing, their bodies were found strewn about their camp. But they didn't seem to be lost. They hadn't frozen to death. Many of them were only half-dressed, in fact - and their tent was ripped open from the inside.
What did they see that was so terrifying that they ripped their way, nearly naked, out of the tent and into the frozen dark?
Why was one of the hikers' bodies discovered nearly ten feet up a tree?
How were two hikers' internal organs nearly crushed, but with no external injuries evident?
Why were two of the hikers' eyes missing?
And why was one hiker's clothing... irradiated?
There have been many theories over the years about the Dyatlov Pass Incident: most recently, the "slab avalanche" theory, which fits better than most. But it still doesn't explain everything, like the radiation.
The true cause may still be out there... waiting.