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

In the episode, John Doggett (Robert Patrick) continues his search for Mulder, and attempts to uncover an alien bounty hunter within their ranks.

FBI special agent Fox Mulder (David Duchovny) is currently missing, having been abducted by aliens in the seventh season finale, "Requiem."

His partner Dana Scully (Gillian Anderson) has been working with Agent John Doggett (Robert Patrick) in order to locate him.

After consulting with The Lone Gunmen, a trio of conspiracy theorists made up of John Byers (Bruce Harwood), Melvin Frohike (Tom Braidwood) and Richard Langly (Dean Haglund), Scully finds evidence that Mulder may be in Arizona.

Doggett receives news that Gibson Praise (Jeff Gulka), a boy with potentially extraterrestrial DNA, may be in hiding in Arizona as well.

The two, along with Walter Skinner (Mitch Pileggi) and a task force of FBI agents arrive and, after searching, find Mulder and Praise on the corner of a mountain.

"[5] Kaplan's task was aided by the discovery of backdrop from the film Alien (1979), which she and director of photography Bill Roe "lit ... very dimly and put ... behind" the chair in which Mulder is restrained.

For the scene in which Mulder's face is restrained by hooks, make-up artist Matthew W. Mungle, who created special cheek prosthetics that were then attached to Duchovny (whom series makeup supervisor Cheri Montasanto-Medcalf later noted "sat pretty good through all that").

Robert Shearman and Lars Pearson, in their book Wanting to Believe: A Critical Guide to The X-Files, Millennium & The Lone Gunmen, rated the episode five stars out of five.

[11] Shearman and Pearson noted that the final scene, featuring Mulder surrounded by the alien bounty hunter was created with "beauty, emotion, and horror which in collision make The X-Files one of the best shows on TV.

Club wrote that both "Without" and "Within" form "a great way to pick up after the cliffhanger ending of the previous season" and that "the pair of episodes [...] work well as an introduction to the new narrative status quo.

[13] George Avalos and Michael Liedtke from the Contra Costa Times praised the episode and noted that the Scully/Doggett dynamic and the hunt for Fox Mulder worked towards the show's strengths.

[14] Tom Janulewicz from Space.com positively commented on Scully's conversion from skeptic to believer, writing, "Regardless of whether it's aliens, flukemen, or pizza delivering vampires, The X-Files is all about phenomena that don't stand in the face of 'rational' explanations.