In late January 1959, a group of ten experienced hikers, mostly students and graduates of the Ural Polytechnic Institute, set out on a difficult winter trek in the northern Ural Mountains. Their leader was 23-year-old Igor Dyatlov. One member turned back early because of illness.

The other nine never returned.

What the search found

Weeks later, searchers found their tent on the slope of a mountain. It had been cut open from the inside. Footprints led away downhill — people in socks, a single shoe, or barefoot, walking in an orderly line, not running.

The bodies were found over the following months. Some were near the edge of a forest, about 1.5 kilometres away, by the remains of a small fire, in their underwear. Others had apparently tried to return to the tent and died of hypothermia.

Four were found last, in a ravine, buried under snow. Some had severe injuries: fractured skulls and ribs, as if hit by great force, but with little external damage.

The theories

For decades, the incident attracted every kind of explanation: secret military tests, a Yeti, attacks by local Mansi people, infrasound, UFOs, and more. Some of these were fuelled by the secrecy of the Soviet era and by strange-sounding details in the files.

In this explanation, the hikers heard or felt snow pressing on the tent in the night, cut their way out in fear of a larger avalanche, and retreated toward the forest — planning to come back. In the dark, the cold and the wind, they couldn't.