In February 1959, nine young adults set out to for a skiing adventure on the slopes of the Ural mountains in Russia. About three weeks later their bodies were found on a mountainside —appropriately named "Dead Mountain" in native language — amid a weirdly captivating set of clues.
When searchers finally found the unfortunate group, they struggled to understand exactly what had transpired. The victims had cut their tents open from the inside and then left the camp area wearing almost no clothes in spite of the sub-zero temperatures.
Investigators soon found two bodies near a tree line and the remains of a campfire. Three more bodies were found farther away. Authorities determined that they likely died of hypothermia.
It wasn't until that May that police found the remaining four bodies, entombed under more than 10 feet (3 meters) of snow in a ravine. Autopsies showed that these victims had serious injuries, including skull fractures and broken ribs, but no external signs of harm, except for the fact that one woman was missing her tongue.
The hikers also tested for high levels of radioactivity. Other hikers and locals reported (and continue to report) strange lights in the sky in the area.
The most likely scenario is that the hikers were caught in an avalanche while they were sleeping and then cut their tents to escape. Terrified, they ran from their campsite without proper gear. Two hikers started a small campfire while the other three tried to return to the tents for warm clothing and the other four wandered on, perhaps lost and suffering from cold-induced confusion.
The internal injuries could well have been caused by the force of an avalanche. The young woman's missing tongue could have been scavenged by animals.
But no explanation really accounts for the radioactivity. Perhaps the group happened upon a secret military testing facility.
If anyone in the Russian government knows exactly how they died, they're not saying. The case was closed and abruptly sealed by the government with a resolution, leading to long-lived conspiracy theories.