The X-Files - Season 4 - Eps 8: Tunguska (1)
Mulder is given a tip about potentially dangerous paramilitary operations on the U.S. soil but during the sting operation is surprised to find out the identity of his mysterious informant - it turns out to be Alex Krycek. Suspicious about his true motives, Mulder reluctantly follows the information provided by Krycek. However, soon he discovers a much bigger conspiracy which takes him to a gulag in Tunguska, Russia where prisoners are being used for experiments involving a substance of alien origin.
About The X-Files

Title: The X-Files
First Air Date: 1993-09-10
Last Air Date: 2018-03-21
Status: Ended
Rating: 8.4/10 (from 3182 votes)
Language: EN
Seasons: 12
Total Episodes: 218
Network: FOX
Genres: Mystery, Sci-Fi & Fantasy, Crime
Production Companies: Ten Thirteen Productions, 20th Century Fox Television
Synopsis
The exploits of FBI Special Agents Fox Mulder and Dana Scully who investigate X-Files: marginalized, unsolved cases involving paranormal phenomena. Mulder believes in the existence of aliens and the paranormal while Scully, a skeptic, is assigned to make scientific analyses of Mulder's discoveries that debunk Mulder's work and thus return him to mainstream cases.
Cast

David Duchovny
Fox Mulder

Gillian Anderson
Dana Scully

Mitch Pileggi
Walter Skinner