In 1959, after a group of nine student hikers are found dead in the Ural Mountains, KGB Major Oleg Kostin is sent to investigate. During the autopsy, Oleg has a flashback of a disturbing memory from WWII. Soon he discovers his first key lead.

Nine days before the group's death, the hikers pass through a small village where they learn about the region's Indigenous Mansi people, who have named the mountain they're headed toward "The Dead Mountain."

Oleg heads to Moscow to look further into the file of Alexander Zolotarev, the oldest member of the group, and makes a surprising discovery about his body. Later he has another flashback from the war and decides to set out for the pass on his own.

As the hikers prepare for ascension, an ominous wind engulfs them, followed by an astonishing sight in the sky. Perplexed, the group begins to remember the words of the Mansi locals before receiving one more warning.

Tempalov and the searchers examine the scene of the group's death, finding multiple confounding details that inspire different theories. Kostin shows his superiors a report that details strange objects in the sky, and a crucial discovery is made.

The group stumbles upon a mysterious man in the woods with suspicious motives. After being questioned by an officer, the hikers seek shelter at a Mansi yurt as a snowstorm approaches. But an incident forces them to leave and brave the storm.

After learning about the prison fugitives, Oleg tries to put the pieces together to close the Dyatlov case. Were the hikers murdered? Or does the answer lie in the supernatural? Meanwhile, Oleg decides to confess his feelings for Katya.

On the group's last night, they reach the pass and set up camp. As the night progresses, the conditions worsen and their struggle becomes unthinkable. Each harrowing detail fills in the puzzle pieces of what really happened to the Dyatlov hikers.