When the helicopter rescue team arrived at the Dyatlov Pass in February 1959, the nine missing hikers had been dead for weeks. The more the investigators tried to piece together what happened, the more the story didn't seem to add up.
Their tent had been cut open from the inside and abandoned, but there was no sign of a struggle. Over a half-mile away, two victims were almost completely naked. Though temperatures were 30 below zero that night.
Other bodies were found even farther away.Two had fractured skulls, two more had major chest injuries, one was missing his eyes; another was missing her tongue. And reports show that two of the hikers had been exposed to unusually high amounts of radiation.
Soviet investigators listed the cause of death as "a compelling natural force," and closed the case a few weeks later. The Dyatlov Pass Incident has been a mystery for over 60 years.
Theories include a military cover-up, a KGB operation gone wrong, a bigfoot attack and of course... aliens.
One researcher believes he knows what happened that night. Others are not so sure.
Let's find out why.