Original subtitles

Fishburne: Tonight, an infamous Cold War cold case.

♪ ♪

Nine hikers found mutilated on a remote mountain slope.

Their injuries and the facts don't seem to add up.

- You can't help but wonder who would be capable of doing this.

♪ ♪

- It looks like a murder scene

from a super graphic horror movie.

Fishburne: Now, we uncover the top theories

surrounding a place that's been called

Russia's Area 51.

- There's a number of people in Russia who believe

that a yeti is the culprit in this case.

- This looks and feels a lot like a coverup.

♪ ♪

Fishburne: Can new evidence

finally bring us closer to the truth?

♪ ♪

- The bodies all appear withered,

and some of them have third-degree burns on them,

which is a sign of radiation poisoning.

♪ ♪

Fishburne: What really happened at Russia's notorious

Dyatlov Pass?

[dramatic music]

♪ ♪

The Soviet Union 1959.

As the Cold War between the U.S. and USSR intensifies,

so do conspiracy theories about covert experiments,

secret weapons, and spies.

And on February 26th, high up in Siberia's Ural Mountains,

something equally nefarious will be discovered.

On that day, three cross-country skiers

spot a solitary tent partially collapsed by snow.

- What was unusual was the entrance was fastened closed,

but the outside had been slashed open.

They looked inside, and they found nobody was there,

but they did find some footprints

leading down the hill.

- And when they get to the end of that trail

they make a horrible discovery.

They find corpses in the snow.

Fishburne: Warning: The images

you are about to see are disturbing.

- Close your eyes and try to picture the scene.

Imagine you're going through the snow.

You come across these bodies.

It looks like a murder scene

from a super graphic horror movie.

It just keeps getting worse and worse.

- The first thing the investigators found

were two members of the team

lying underneath a cedar tree,

and neither of them were wearing winter clothes.

They were just in their underwear.

One has burns on his head and foot.

There's lots of cuts and bruises on his body.

- He has some dried blood on his face and also strange,

gray foam is found on his cheek.

- It looks like this could be foul play.

The second body has similar cuts and bruises.

He's missing the tip of his nose,

and his knuckles are bruised and swollen.

It's a very strange scene.

Fishburne: Several yards away, another body.

- This third body is found lying face-up in the snow.

He's hugging a branch.

He also has cuts and bruises on his knuckles

and dried blood on his face,

and he's facing back towards the tent,

suggesting he's trying to make a desperate attempt to return.

- So naturally, the skiers rush to report this,

and a bigger search party is put together.

And this bigger search party starts combing the area,

to try to find clues as to what happened

to these three men.

But before they can figure that out,

several more bodies turn up.

Fishburne: Next, they discover a young woman.

- She has a lot of bruises on her face,

and her hair is in disarray.

- She has this long, red bruise on the side of her torso,

and on top of that, her fists are clenched,

so it looks like maybe there was some sort of scuffle.

Some sort of fight that might have went down.

You also have to remember this is Siberia.

You've got freezing temperatures.

You've got blinding snow, so all this work

that the search party is trying to do,

to locate all of this evidence, make the work

very, very slow and very, very difficult to perform.

Fishburne: After a week, a fifth corpse is found,

further up the slope.

- It's another young male victim,

and this one has a fractured skull.

Perhaps more evidence

that there was some violent altercation.

What's interesting about this victim

is he had one sock on one foot and a felt boot on the other,

suggesting something took him by surprise.

Fishburne: Six weeks later, as the snow starts to melt,

the mystery deepens.

Members of the Mansi, a local indigenous tribe,

approach the police and lead them

to a makeshift snow shelter

250 feet from where the first two bodies were found.

- The searchers--they start to dig below the surface,

and they find this snow den

with these branches all lined up

next to each other forming some type of floor.

Additionally, they're also finding

some torn pieces of clothing.

There's a pair of sweatpants with--[slicing]

The right leg just cut off completely.

Likewise, there's also only the left half of a woman's sweater,

so there's more and more evidence

that's starting to build

that something violent may have happened here.

Fishburne: Investigators excavate

around the snow shelter,

revealing four more victims,

bringing the death toll to nine.

- These four bodies are lying somewhat closely together,

in the bed of a rocky stream, at the bottom of a ravine.

It looks like a dumping ground.

It looks like just someone or something

may have dropped them there.

Fishburne: Compared to the other victims,

these bodies have even more ghastly injuries.

- One corpse is a male victim with a severely twisted neck.

- Another young female has a crushed ribcage,

and it's such a brutal injury

that her ribs actually punctured her heart.

And horrifically, her eyes and tongue are missing.

Another young male has a massive fracture

to the side of his skull that would have

almost certainly knocked him unconscious.

- It looks more and more like the injuries

are from brutal beatings from some heavy, blunt object.

Fishburne: Investigators soon identify the dead

as members of an expedition sponsored

by the Ural Polytechnic University.

They were reported missing

after failing to complete their trip.

- Once you know who these victims are,

it's even more tragic.

These students were among the best

and the brightest from the Ural Polytechnic University.

- They were very experienced mountaineers

and well-respected members of the sports club

of the Ural Polytechnic Institute.

Fishburne: The group's leader is 23-year-old

engineering student Igor Dyatlov.

The tragedy bears his name.

- The Dyatlov Pass is named in memory of Igor Dyatlov.

- He designed this expedition

to be as challenging as possible,

so they could all get certified

as grade III outdoorsmen.

This was the highest category in the Soviet Union

at the time.

Fishburne: In January, the group leaves their home

of Yekaterinburg

and travels to the village of Vizhay.

- From Vizhay, they go off grid

and head off into the wilderness.

They have a compass and all the gear they think they need,

but they don't have any radio communication equipment

with them.

Fishburne: The trip was supposed to cover

200 miles over 16 days,

but they only make it halfway.

- What frustrates friends and family of these hikers

the most is that they say that they are way too smart

and way too experienced to have ended up

accidentally freezing to death in the outdoors.

Fishburne: The lead investigator in the case,

Lev Ivanov, says he knows the cause of death.

♪ ♪

- There are signs of a struggle at the scene,

and no one can ignore the bruises

and cuts to the face, and the body,

and the missing pieces of flesh.

Fishburne: But who could be capable

of such a violent crime here?

The potential suspect list is incredibly short.

- The mountain where the tent was abandoned--

It's called Height 1079--

Is a mostly uninhabited area,

and it borders the Siberian wilderness.

Almost nobody lives there.

Almost.

Except for the fact that this region is home

to many of Stalin's infamous gulags.

Stalin built lots of gulags.

If you don't know what a gulag is,

it's this insane labor camp

where political prisoners were sent.

They were forced to do hours upon hours of manual labor.

This is where you have some of the most hardened criminals

in the Soviet Union residing,

so investigators are thinking maybe one of these prisoners

got out and encountered those nine hikers.

Fishburne: Especially when they learn

that the Ivdel Gulag is only a few miles

from the site of the attack.

- Police check with the Ivdel Gulag,

to see if there are any prisoners that are missing,

but no, they're all accounted for.

They also doubt any escaped prisoners might have done this,

because no provisions or belongings

were stolen from the tent,

so the escapee theory doesn't go anywhere.

- So investigators start to ask, "Okay.

It seems like it's a very personal crime."

So they start to wonder,

"Could this have been connected with anyone

that was affiliated with that group?"

And one name pops up.

Fishburne: The name? Yuri Yudin,

a tenth hiker with the group and the sole survivor.

Is it possible that members of the Dyatlov expedition

were killed by one of their own?

[percussive music]

♪ ♪

Fishburne: It's a mystery that's gripped the world.

Nine Russian hikers dead in a remote mountain pass.

Police are certain it's murder,

and among their top suspects is fellow hiker Yuri Yudin.

- So Yuri Yudin is a fourth-year engineering student

who was part of that same group of hikers.

In fact, he's the tenth member of that group.

But apparently, Yudin left early,

and instead of ending up dead, he's now the sole survivor.

Therefore, we can assume one of two things.

Either Yudin is incredibly lucky,

or he's the killer.

♪ ♪

Fishburne: When Communist Party officials

question Yudin, he tells them

he backed out of the trek long before the murders.

- Yudin claims to investigators

that his back started to hurt when he was

making his way up the mountains,

which caused him to quit the expedition.

He says that he left the group on January 28th at 11:45 a.m.

at a location known as the 2nd Northern,

and when he leaves, the rest of his group

are all still very much alive.

Very much breathing.

But as investigators are questioning Yudin,

they start to notice he becomes a bit more panicked.

A bit more nervous. They're certainly skeptical.

Fishburne: Still unsure of Yudin's story,

investigators ask him to help analyze the crime scene.

- And this has to be traumatic for him.

Think about it.

He was supposed to be on that expedition with them,

but because of his bad back, he ends up going back.

And now, he's the only one alive, of all of his friends.

So when he gets to that crime scene

he acts with genuine shock and surprise.

- Yuri notices something the police couldn't have.

That some of the clothes found on the bodies of those

in the ravine belonged to some of the other students.

Fishburne: It's another bizarre detail,

in a case full of them.

The clothing is sent to a laboratory for analysis.

While they await results,

investigators tried to verify Yudin's alibi.

- Yudin's story of a bad back checks out.

Yudin was in his native village of Yemel'yashevka

with his family on February 1st and February 2nd.

The same dates that investigators calculate

as the time of death.

Fishburne: If Yudin's not the killer,

who else could be?

The only other known group of people in the area

are the Mansi.

- The Mansi have helped with the investigation.

And they're the ones that pointed the investigators

to the four bodies in the ravine.

Fishburne: Despite that, Lev Ivanov

starts looking into the group.

♪ ♪

- So Ivanov thinks that the Mansi are upset

that a group of outsiders set up camp on Height 1079,

also known as Kholat Syakhl,

which roughly translates to Dead Mountain.

- The explorers are violating sacred Mansi territory,

and even more sacrilegious,

there are two women in the group.

And for the Mansi, women are forbidden to even

step foot on sacred land, let alone look at it.

Maybe that's why the eyes are removed

from a couple of corpses.

Fishburne: Ivanov interrogates multiple tribe members.

While they deny involvement, they offer a new detail.

- Several people tell the same crazy-sounding story

that the Mansi saw lights in the sky

or burning fireballs in the sky,

on the very night that the hikers died.

Police recovered a camera from the campsite,

and the last photo on this camera

had an image they didn't understand.

It looks like flares or streaks in the night sky.

It's hard to tell,

but could this corroborate the lights in the sky

that were supposedly seen that night?

There are no timestamps on the photo,

and if this is the last thing the hikers photographed,

you can't help but wonder

if this has something to do with the incident.

Fishburne: Without a confession

or any evidence that points to the Mansi,

Ivanov has no proof.

- So that's where things remain for a while, at a standstill.

No new evidence, and no new suspects.

Nothing to explain what happened to the nine hikers.

Fishburne: Until several weeks later,

when laboratory results come back.

- And just when you thought it was done,

here's a new chance to find some new leads

and to keep investigators moving forward.

The analysis of the ripped clothing

that was found in the ravine comes back,

and it reveals an incredible new clue.

- The analysis shows there's some unusually

high levels of radioactivity on some of the items.

♪ ♪

Fishburne: But how could clothes

from alleged murder victims be radioactive?

The answer could turn the course of the investigation

in an entirely new direction.

- But that's not what happens.

Instead of following this new lead

and getting to the bottom of the mystery,

authorities go ahead and do the exact opposite.

On May 28, 1959, three months into this investigation,

and after finding this new evidence,

Lev Ivanov abruptly closes the case unsolved.

The Soviet government seals off the entire area

known as the Dyatlov Pass

and prohibits anyone from going there.

Fishburne: Ivanov's report marks a change.

He now states that all nine deaths

were caused by an unknown elemental force

which they were unable to overcome.

But while Lev Ivanov seems to want this

to be the final word,

it won't be.

Fishburne: When nine hikers die

under mysterious circumstances during the Dyatlov expedition,

the public is eager to find out why.

But lead investigator Lev Ivanov

abruptly closes the case, after three months,

just as he received shocking evidence.

The victim's clothing shows radioactivity.

- This is a crazy detail

that definitely deserves some digging,

so as soon as a case like this is shut down,

people immediately think that it's a coverup.

Fishburne: The question is why?

♪ ♪

- The USSR wants to be the dominant superpower,

so they're doing a lot of covert things at this time.

They're doing research experiments.

They're doing military experiments.

They have spy operations going on.

Government coverups are happening every day.

- The Soviet population understands

that there are secret tests,

but also they accept the rule of the government.

That this is secrecy they cannot know about.

- I mean, it's not hard for people

to put two and two together.

You got the Dyatlov deaths and now the appearance

of unusually high levels of radiation

on some of the clothes.

People are starting to think

that this is linked to the military.

Fishburne: At the victims' funerals,

friends and family remark

that the cadavers have an unnaturally orange appearance.

- The bodies all appear withered,

and some of them have third-degree burns on them,

which is a sign of radiation poisoning.

Fishburne: The family of group leader Igor Dyatlov

say they are certain the military was somehow involved.

But exactly what are they covering up?

- Don't forget the Mansi said that they saw fireballs

in the sky that night,

so one idea is that it's a case of a weapons test

that goes wrong.

The rocket fails to go into orbit and lands

really close to where the Dyatlov hikers

are camped out for the night.

And it sends shockwaves, which frightens them,

and it has them running out of the tent.

- A different hypothesis.

Some think that it was the Soviet government

or its military that killed them,

because they witnessed something

they were not supposed to have witnessed.

- And there's one other little detail

that seems to prop up this coverup theory.

It's presumed that one of the hikers is actually a KGB spy,

and his name was Semyon Zolotaryov.

♪ ♪

Fishburne: Zolotaryov is the only person on the expedition

who is not a student.

In fact, he's 38 years old

and mysteriously added to the group

by Communist officials at the last minute.

- A lot of things about Zolotaryov are a bit unusual.

For one, he's single,

which is kinda weird in Russia at this time.

Additionally, he's got all these very cryptic tattoos

on his body.

And at the start of the journey,

this older gentleman

tells the students to call him by a fake name: Sasha.

- We do know that Semyon Zolotaryov

is not who he pretends to be.

There's too much in his biography

that is not consistent.

Even when he talks about his service in World War II,

he mixes up dates when he served in one unit or another.

And in my opinion, having studied this case,

he was a top-notch KGB operative.

- So the theory is that the KGB

is spying on the Russian military,

to see what is going on in these mountains.

And unfortunately, these hikers just got caught in the middle

of an interagency conflict.

- So Zolotaryov is found out to be a spy agent,

on behalf of the KGB.

So the group, although innocent,

are killed because of him.

Fishburne: When Zolotaryov's body is recovered,

the film in his camera has been destroyed

by water damage.

His motivation and his potential KGB ties

remain a mystery.

- Whether the KGB was connected to the case or not,

we don't know, but the idea of

the military being involved in the whole mess

is very much popular

and one of the top hypotheses in this Dyatlov Pass incident.

- Even the university,

the Ural Polytechnic Institute,

which sponsored the hike, thinks this is what happened.

Fishburne: And in 1990,

another familiar voice joins the chorus claiming a coverup.

- Lev Ivanov published an article

with a strange title "The Mystery of the Fireballs."

And he hinted that he was under pressure to close the case

and not to continue to look into the cause of the death.

- Communist Party officials were incredibly worried

that these reports would leak out to foreign nations,

and on top of that, Ivanov believes

that it's these secret tests

that ultimately leads to the deaths of these hikers.

Fishburne: Sole survivor Yuri Yudin also believes

the government was involved

and reveals a key piece of evidence

before his death in 2013.

- Yuri says that when he was helping the investigators

with the inventory of the items left

by the hikers, things didn't add up.

He found things that did not belong to anyone,

like a military cloth, a pair of glasses,

also an extra pair of skis.

And his gut feeling was that this was staged.

Fishburne: Even Boris Yeltsin thinks authorities

are hiding something.

When he's made President of Russia,

after the fall of the USSR, in 1991,

he promises to investigate the Dyatlov Pass incident.

- He was very much interested in the case, as well,

because he was himself

a graduate of the same institution,

Ural Polytechnic, and because people appealed to him.

- He uses all of his political power

to try to find information,

things that happened in 1959

that can shed light on this event.

Now the closest missile launch site

to the Dyatlov Pass

is actually located in Kazakhstan,

and it's called the Baikonur Cosmodrome.

Yeltsin's investigators dig into the records of Baikonur,

to see if there were any missile launches in 1959

during that window of the hikers' death.

- He assured people that there were no rockets during the day

when the hikers perished.

- It's tough to know if he actually did look into this,

but if what he's saying is true,

there were no missile tests

that happened in the area during that time.

- Whatever Yeltsin's involvement with the case was,

it didn't bring us any closer to finding the truth.

Fishburne: Yeltsin's findings

seem to end the coverup theory,

but they don't stop the public from asking questions.

And a shocking new one is about to emerge.

[tense tone]

♪ ♪

Fishburne: After the fall of the Berlin Wall in 1989,

the Dyatlov Pass case files are finally made public,

giving amateur investigators a fresh chance

to solve the mystery.

Digging deep into the evidence,

they find an intriguing photo taken by one of the hikers,

and it leads to a shocking new theory

and a surprising suspect.

♪ ♪

- There's a number of people in Russia

who believe that yeti,

or snezhnyy chelovek, in Russian,

is the culprit in this case.

In one of the photographs found at the site,

there is a very unusual creature

that was detected in the photograph,

and it's very interesting.

This was the last frame of the photographs Nikolay Thibeaux

took at the site,

and I don't think he had enough time

to think what he photographed,

but it's there, historical evidence.

What you see in the picture is a humanoid-like being.

It's big. It's about 10 feet.

It's hulking, much like the yetis or snowman have,

and it looks like it's looking at the group,

observing them.

♪ ♪

There were so many stories

coming from different parts of the Soviet Union,

and this photograph could definitely serve as a proof

that the yeti is out there.

The yetis are huge beings.

About 10 feet in size.

People are afraid of them,

because they could crush with their arms and legs

a human being and do it very quickly.

Fishburne: Even the Dyatlov students

themselves make reference to a yeti prior to their trip.

- Before they hike into the mountains,

the students, the hikers

published a satirical newspaper.

And they write a headline that reads:

"Latest evidence indicates that the yeti lives

in the Northern Urals, near Mount Otorten."

It's quite possible that

while they wanted to express themselves

and show no fear by placing jokes in that newspaper,

they knew that something was out there,

and it could be yeti.

♪ ♪

Fishburne: Supporters of the yeti theory

also point to photos of the bodies

that show what appears to be abject terror

with clenched fists ready for a fight.

- Of course, seeing a horrible creature like a yeti

by their tent, that would have frightened them.

♪ ♪

Fishburne: But that's not the only creature

that could get such a reaction.

- We have to account for many predators that live in the area

that could have attacked the hikers,

and among them are bears, wild dogs, wolverines,

even the Siberian tiger.

- But the most likely culprit in the animal attack theory

is a brown bear.

- The autopsy report listed fractured skulls, broken chest,

scratches and cuts, and even missing flesh.

A brown bear would be capable of doing this,

but the problem with the brown bear theory

is that they were in hibernation around this time.

- That's all the more reason if a bear wakes up early

and is hungry, it would seek out nine campers

that just happen to be in that area.

Fishburne: After decades of public speculation

about animal attacks, homicide,

coverups, and much more,

in 2019, public fascination with the Dyatlov case

prompts Russian authorities to finally reopen the file.

A young prosecutor, Andrei Kuryakov,

takes the lead.

- Andrei Kuryakov sits down with a list of 75 theories.

Thanks to the growing public interest,

this case has gotten bigger and bigger.

Not sure if the yeti has made the list,

but Kuryakov certainly has his work cut out for him.

But it seems he's up for the task.

Fishburne: As Kuryakov starts researching,

he notices a detail that leads to a new theory.

♪ ♪

- It turns out that the weather on the 1st of February,

in 1959, is pretty extreme, for that mountain,

with winds up to 65 miles an hour

and temperatures down to 30 degrees.

And this has Kuryakov thinking, "Could it be an avalanche?"

Fishburne: Andrei Kuryakov organizes a 2020 expedition

to the Dyatlov Pass to test his theory.

♪ ♪

And he's about to find one key piece of evidence

that the original investigation got wrong.

Fishburne: 60 years after the Dyatlov tragedy,

prosecutor Andrei Kuryakov returns to the crime scene

with new technology

hoping to prove the killer was an avalanche.

- So they used photogrammetry to really pinpoint

the location of the tent,

and then they take photos of the current landscape

and compare 'em with the old ones.

And they notice a huge discrepancy

of what they originally investigated.

- The location where the tent was pitched in 1959

is actually several hundred feet away

from where they originally thought it was pitched.

- The location of the tent is the #1 factor in determining

if an avalanche took place,

and it looks like the original investigation

might have made a mistake.

♪ ♪

Fishburne: The risk of an avalanche

depends on the degree of incline.

On average, it takes a 30-degree incline

to trigger one.

- Using the old incorrect data,

investigators prior to 2019,

thought that the slope above the tent was about 15 degrees,

so they've ruled out the avalanche theory

this entire time.

Fishburne: The newly-calculated location

has a much steeper slope of around 28 degrees.

- It's still not 30 degrees.

An avalanche still may not be possible,

but with the right weather conditions,

it's much more likely.

When they analyze the weather conditions,

they find that there's a special phenomena here

called katabatic winds.

Katabatic winds travel at hurricane speeds.

In effect, they act as a huge snowplow.

These winds can take tons and tons of snow,

and it's very likely that these winds could have

deposited huge amounts of snow above the hikers' tent.

And that's when they become even more confident

in their avalanche theory.

They think that this mountain is a death trap

just waiting to spring.

♪ ♪

Fishburne: Once the weather expedition is complete,

Andrei Kuryakov presents his findings to the public.

- Kuryakov theorizes that it's sometime after the tent

was set up around 7:00 p.m.,

a wind storm kicks off into high gear.

- Sometime between 1:30 and 5:30 a.m.,

a small avalanche is triggered above the tent

where they had cut into the slope.

- That new snow up above is too heavy,

and it crashes down onto the tent.

After that initial snow dump, the hikers,

fearing more is to come,

cut their own way out of the tent

and run to a rocky ridge 150 feet away.

- This is, at the time, standard avalanche protocol--

The idea of being able to find a safe place

behind a high, rocky ridge

that would redirect the snow away from them.

Fishburne: But here, Kuryakov's theory

takes an interesting twist.

- He doesn't actually think a bigger avalanche ever hit.

He thinks that they hurried out of the tent,

but it never came.

And the problem is that the hikers got disorientated,

and they couldn't find their way back to the tent.

- So the investigator tests his theory.

He blindfolds a man and a woman.

Makes 'em walk 90 feet away from the tent,

and then challenges them to find their way back,

and they can't.

Fishburne: And what about their strange

lack of clothing?

- Kuryakov thinks that some of them

were partially undressed when they fled the tent,

but he thinks the others may have suffered

from a phenomena called paradoxical undressing.

And this is where people,

in their final stages of hypothermia,

feel as if they're burning hot,

which leads them to take their clothes off.

Fishburne: According to Kuryakov,

sometime between 4:30 and 7:30 a.m.,

the hikers freeze to death.

- The two young men found in their underwear

under the cedar tree died first.

The other members of the group

cut the clothes off of their dead friends,

in a last-ditch effort to survive.

At some point, the group splits up,

and three of them-- Dyatlov, Kolmogorova,

and Slobodin--head back towards the tent.

Sadly, they freeze to death before making it back.

Fishburne: But what about the final four?

- And this is where the theory gets really weird.

You can never believe this group had such bad luck.

The last four dig down a snow shelter--

Basically a snow chamber

where they can hide from the elements

and share body heat.

But the one spot they decide to dig in

is above a stream through a hollowed-out icy tunnel.

They dig down, and the tunnel collapses.

They fall into the icy stream

and are buried under 15 feet of snow.

Fishburne: As he concludes the press conference,

Kuryakov declares that the Dyatlov Pass mystery

is finally solved.

- The Russians are outraged at Kuryakov

and loudly reject his theory.

The families of the dead are especially critical of him.

- Let's be clear. The public hates the avalanche theory.

It doesn't account for so many key facts

and details of the case.

- People were making fun of it and disregarded it

because they know this is another set of coverups.

Fishburne: The Dyatlov Pass incident

has spawned many theories over the years.

But in a case full of strange details and unusual twists,

none have fully aligned with the facts.

- You can say maybe it's a bear attack,

but the bears are hibernating.

You say it's an avalanche,

but what about their clothes testing positive for radiation?

What about the Mansi tribe's testimony

of fireballs in the sky?

What about Semyon Zolotaryov, the possible KGB agent

that was planted among the hikers?

There are just so many details to account for,

and there isn't just one theory that makes total sense.

Fishburne: But what if there is?

♪ ♪

- So theory after theory after theory comes out,

and after a while, people just stop

looking at all the evidence one piece at a time,

and they just say to themselves, "Well, what if

it's not just one thing?

What if all of these theories are partially right?"

♪ ♪

So in other words, it's an avalanche,

and it's a murder, and it's a coverup,

and it's an animal attack, all in one.

- If you start with the fireballs

reported by Mansi during the time,

it could be part of a nuclear experiment we don't understand.

Maybe a new type of nuclear weapons

that the KGB, of course,

did not want to leak out to its enemies in the West,

and they covered it up.

Apart from Semyon Zolotaryov,

the others students-- Those poor students

did not know they were heading

into this special testing area.

This could explain the radioactivity

that was found in their clothing.

♪ ♪

Fishburne: A nuclear test may also explain the avalanche.

- Those nuclear weapons emit shockwaves.

Those shockwaves are the catalyst

for the avalanche to collapse on the tent,

and it could have caused those blunt force injuries

on their own.

So in the span of an instant,

the explosion startles the hikers.

It starts the avalanche. It showers them in radiation.

The shockwaves hit them with the force of a speeding truck,

which causes injuries, and it causes them to rush

and escape down the side of a mountain.

Fishburne: From there, the coverup.

- If any of the hikers would have survived,

the military could have taken care of them,

because they didn't want eyewitnesses to something

that is top secret.

- And even if they were dead,

the lead investigator, Lev Ivanov,

was forced to close short the investigation,

so nothing is leaked out.

- And finally, the animal attack theory,

of course, accounts for injuries

that hikers had sustained,

because the animals had access to the bodies

for a period of time,

and they did what animals do.

They ate into the hikers' cadavers.

- What if it's a combination of all of these things

that could have happened to these nine hikers?

That's what the Soviet authorities

are trying to cover up.

- No matter how the hikers died, if there was a coverup,

their blood is on the hands of the Soviet government.

The Dyatlov Pass incident is the greatest mystery

and unsolved case in Russia,

but the government doesn't make

any more efforts to solve it.

So it is all up to us now,

amateur researchers and investigators,

from all over the world,

to uncover what really happened.

♪ ♪

Fishburne: In 2020, the Dyatlov Group Memorial Foundation

published a letter in support of the all-in-one theory.

For the families of the students killed

on the mountain that night,

that small vindication will have to suffice, for now.

Because when it comes to the truth of this mystery,

the secrets are buried incredibly deep.

I'm Laurence Fishburne.

Thank you for watching "History's Greatest Mysteries."