The year is 1959, the month is January.
Ten experienced hikers start a journey through a Russian pass.
One turns back, complaining of medical ailments. The rest journey on.
The snow becomes heavier. A storm arises.
In the confusion, they get lost.
Twenty days later, still no message from them has reached their families. A search begins.
After regular rescue teams are unable to find them, the military gets involved and sends out helicopters. They find this:
The tent is torn open from the inside.
Later, they find the corpses.

Two are below a tree.
The tree shows signs of being climbed. The remains of a fire are at their feet.
They are clothed only in their underwear.
They died of hypothermia.
Another is found—this one female, in a stream. Her hands are macerated. Her tongue and eyes are missing. She too, has died of hypothermia.
The rest are found just a few paces away. They are wearing clothes, but they are the clothes of the other hikers. Two have died of head trauma. The rest, hypothermia.
What killed them?
Theories have floated around for decades, anything from an avalanche to a Russian yeti claims to be the explanation.
But what really happened?
Rumors of a tribe of people in area being responsible are talked about, but there weren't enough footprints at the scene.
As for the yeti, again, no footprints. And any animal would rule out completely, given that there were hardly any external injuries. 
Avalanche? Improbable.
Not enough disturbance in the snow, and even if they were worried one might be oncoming, that would hardly explain the nakedness and inability to go back to their camp.
My theory is this: one of their own turned on them.
Human intention seems to be the most likely case here—very possibly against one specific person.
Who? The woman.
The only woman on the hike—and very odd injuries indeed. Tongue and eyes gone? That can't be explained by an avalanche.
Violent behavior such as this is isn't unheard of in cases of insanity. The fact that only one victim was in such a state—and even more so that the victim happened to be a woman, suggests some personal bitterness may have been involved.
Who did it?
Well, my guess would be one of the two who died of head trauma.
The others had time to freeze to death—so they must've gotten rid of the killer quickly.
This is, in my own eyes, the most probable scenario.
Another possible theory includes military involvement—this was towards the end of WW2 and the beginning of the Cold War, so it's very possible a confusion happened, or, as they were lost, wandered onto some military grounds by mistake.
Will we ever know what really happened? Probably. Maybe. Maybe by the time we can find out, we won't care.
But I stand by my theory.