The installment explores the series' overarching mythology and is the conclusion of a two-part episode revolving around the final revelation of what really happened to Fox Mulder's (David Duchovny) sister, Samantha.

The episode received mostly positive reviews from critics; many felt that the final reveal was emotional and powerful, although some were unhappy with the resolution.

The show centers on FBI special agents Fox Mulder (Duchovny) and Dana Scully (Gillian Anderson) who work on cases linked to the paranormal, called X-Files.

[4] In the previous episode, "Sein und Zeit", Mulder and Scully tracked down a serial killer who targeted children.

[5] Mulder and Scully aid the Sacramento Police in the investigation of a brutal murder committed by Truelove, the owner of the Santa Village.

Scully finds a 1979 police report of a girl matching Samantha's description, and learns that she was taken to a hospital emergency room.

"[3] "Closure," written by series creator Chris Carter and executive producer Frank Spotnitz, brought an end to Mulder's quest for his sister, Samantha, who had been abducted when he was a child.

While the idea to close the story arc received mixed reactions from various production and crew members, many realized that the time had come for the show to answer one of its biggest questions.

Spotnitz explained that, "I think [series star, David Duchovny] grew tired of playing the man who is missing his sister.

[8] To create the scene featuring the ghosts of the dead children interacting with the characters, various layers of film had to be overlaid onto each other.

[7] Rebecca Toolan traveled to Los Angeles from Vancouver specifically for this episode and "Sein Und Zeit".

Manners played the part of the hypnotist in the video that Scully watches, with the director-turned-actor later noting, "I only act when you can't actually see my face".

"[7] Composer Mark Snow described his score as possessing a "sense of biblical fervor and religiosity—an elegy—a feeling about it that was so poignant and touching to me.

"[9] "My Weakness", a song by Moby from his 1999 album Play, is used in this episode, first when the FBI discover the mass grave and finally at the end when Mulder encounters his sister's spirit.

[13] Furthermore, she argues that because "Closure" opens with the tagline "Believe to understand", Mulder must "take the leap of faith" in order to find enlightenment, and ultimately the truth about his sister.

[14] The first half of the episode plays out according to the tagline; Mulder first believes in "his desire stated in the opening voiceover", and then finds closure.

In "Paper Hearts", a father of a victim notes that the uncertainty of his daughter's murder allowed those who were involved to "consider the possibilities, both for the best and for the worst".

Conversely, Mulder holds onto the possibility that Samantha is alive through much of the series, but when he realizes that she is indeed dead in "Closure", hope is removed but in its place is found peace.

To parallel Mulder's acceptance, Harold Piller refuses to believe his son is dead; as such, he "cling[s] to the possibility [because] uncertainty allows him hope.

Tom Kessenich, in his book Examinations: An Unauthorized Look at Seasons 6–9 of the X-Files, opined that the episode worked best "if some of the previous Samantha-related clues were forgotten", such as when the Alien Bounty Hunter told Mulder that she was still alive in "End Game".

He was also complimentary towards "the ethereal quality of the final few moments", writing that they "lifted this episode up and made it one of the season's most memorable".

"[19] Jeremy Conrad from IGN referred to the episode as "excellent" and noted that a large portion of The X-Files mythology ended with the resolution of Samantha's abduction, saying, "['Closure' is] a final, and concrete, answer to the single thing that was driving Mulder for the entire run of the series.

[23] Meghan Deans of Tor.com felt that the story was "silly", but that, when paired with the idea that Samantha was truly an innocent victim, successfully becomes a "comfort".

"[24] Robert Shearman, in his book Wanting to Believe: A Critical Guide to The X-Files, Millennium & The Lone Gunmen, rated the episode four stars out of five, and called it "brave".