No one knows for sure what actually happened to the trekkers but the most plausible and likely theories are the ones that are dramatised here and presented as the conclusion in the final episode.
The series cleverly uses two styles to tell its story. The hike is shot in black and white and the subsequent investigation is filmed in colour. Flashbacks and backgrounds of the characters are also shot in colour.
The back stories of the older characters mainly concern the war and are completely fictionalised to impart a sense of creepy horror to the series. The indigenous people, the Mansi, are also portrayed as shamanistic communers with nature whose superstitions mesh with the account but are not the cause of the tragedy.
There are hints and suggestions of darker political and military forces at work - this is now in the public domain - which unfortunately led to a rash of conspiracy theories. However, the conclusion reached by the initial and the subsequent investigations seems to be sound and that's the line taken by this programme.
There is enough information made public for the programme makers to have been able to reconstruct most of the hike and the investigation. The conversations are fictional, of course, and the reconstruction of the final hours has, of necessity, to be speculative.
It's a worthy series to watch. The director managed to convey the flavour of the Communist times with élan and accuracy. I didn't quite binge watch, but I had seen all eight episodes within three days. I'm glad I saw this.
