The X-Files - Season 9 - Eps 16: William
Doggett catches someone in the X-files office trying to steal documents pertaining to Mulder's sister. The intruder is a severely scarred man who blames his disfigurement on Government conspirators. He claims the source of that information - and, in fact, the one who helped him gain entry - is Mulder. Although he refuses to divulge the missing agent's whereabouts, the mystery man has enough knowledge of the X-files and its history to lead Doggett to suspect that he just might be Mulder himself. Scully's fears for the safety of her son are elevated when he is injected with an unknown substance. With the mystery surrounding William becoming even darker, Scully must allow herself to send him away for his own safety.
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