The series was created byChris Carter.

The best episodes ofThe X-Filesmake it clear just why the show was so successful and enjoyed such longevity.

Carter wrote and directed the episode.

10-Best-‘The-X-Files’-Episodes,-Ranked

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And while the episode is clearly addressing Mulder and Scullys relationship, its also very much about loneliness.

The team quickly discovers black nodules around swollen lymph nodes are a telltale sign of infection.

The others then suspect Mulder has been infected, leading to increasing tension and distrust in the group.

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On top of being an overall great episode, its also memorable for its tension between Mulder and Scully.

It was written by Carter.

And in trueX-Filesfashion, it raises just as many questions as it answers.

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And, of course, its no surprise that Scully is the one to realize Mulder isnt quite himself.

Despite its commentary on conformity and not-so-forgiving take on suburbia, its one of the more lighthearted episodes.

The episode was written by Vince Gilligan, who also penned some of the series other standout episodes.

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The episode was written and directed by Carter.

The episode was written byDarin Morganand marked his final writing credit in the series.

Morgan is also the writer behind some other notable X-Files episodes, particularly more comedic ones.

X-Files - How the Ghosts Stole Christmas

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Meanwhile, in the present, Scully is desperately searching for him.

Memento Mori is among those standouts,with an incredible performance from Andersonit won her a well-deserved Emmy.

NEXT:The Most Terrifying Monsters in ‘The X-Files,’ Ranked

Gillian Anderson and David Duchovny talk with scientists at research lab in episode Ice from The X-Files

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David Duchovny as Special Agent Fox Mulder, FBI, at a cluttered desk in the pilot episode of The X-Files.

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David Duchovny as Mulder and Michael McKean as Morris switch bodies in episode Dreamland Part 1 from the series The X-Files

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David Duchovny as Mulder and Gillian Anderson as Scully in the episode Arcadia from the series The X-Files

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Mulder (David Duchovny) and Scully (Gillian Anderson) remember events differently in episode “Bad Blood” from the series ‘The X-Files.'

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X-Files - Jose Chung’s From Outer Space

David Duchovny, William B. Davis, and Gillian Anderson in The X-Files, Triangle

Scully and Mulder embrace in hospital in the episode “Memento Mori” from ‘The X-Files’

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