The X-Files - Season 5 - Eps 19: Folie à Deux
Mulder is held hostage inside an office where a man claims his boss is a monster and has clouded all their minds while he turns them into zombies one by one, which is disbelieved until Mulder opens his mind and allows himself to see it too.
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