This is The Guardian.

This holiday season, we've been revisiting some of our favorite episodes from 2021,

and today we're replaying an episode from Guardian Australia's brilliant daily podcast,

Full Story. It's a tale of how nine experienced hikers were mysteriously killed in Russia's

Ural Mountains. Conspiracy theories circled for years, but an unlikely pairing of science

and the movie Frozen may have helped solve the cold case.

I'm Laura Murphy-Oats and this is The Full Story.

So the mystery is known as the Diablo Pass. It began in the winter of 1959 in the Soviet Union

near the Ural Mountains, which is incredibly cold. It's a sort of place that you'd only

want to go to if you really wanted to test your limits.

Robin Andrews is a volcanologist and a freelance journalist.

10 people from nearby university wanted to somehow spend two weeks, sixteen days,

skiing and hiking for 200 miles across this mountain range. There were eight men and two women,

and they all very experienced mountaineers. So how did this trip go?

I mean it went terribly. It went as terribly as any trip could go.

So I've come up to the pluck. There's it's covered in snow,

takes them as snow. There's a portrait of a young man. It's a very Soviet looking design,

the young man in profile. He's looking forward into a bright future.

And then higher up it says in this mountain pass on a freezing night on the 2nd of February,

some tourists from the Ural Polytechnic Institute died.

The story of this trip and what happened on that mountain in 1959 is Russia's biggest unsolved

mystery. It's spawned conspiracy theories ranging from aliens, yetis and secretive government

...