"Underneath" is the twelfth episode of the ninth season of the American science fiction television series The X-Files.
The show centers on FBI special agents who work on cases linked to the paranormal, called X-Files; this season focuses on the investigations of John Doggett (Robert Patrick), Monica Reyes (Annabeth Gish), and Dana Scully (Gillian Anderson).
In this episode, Doggett is determined to find an error in the DNA evidence that freed the convicted Robert Fassl, the "Screwdriver Killer", whom he nearly caught in the act 13 years earlier.
Reportedly, the episode contained "so many problems" that the Fox executives nearly refused to allow the finished product to air.
After being released, he stays in a room belonging to his lawyer, Jana Fain, where he clutches a Rosary beads and prays frantically.
After hearing of Kaylor's disappearance, Reyes theorizes that Fassl's piety and his unwillingness to acknowledge his darker half has given him the unwanted ability to physically change into another, more violent person.
[2] According to Shiban, the series' production staff had "actually talked for some time about doing a Jekyll/Hyde story but never quite found a way to do it" until the idea to use DNA came into play.
[5] Shiban originally wanted to film the sewer scenes in Los Angeles' actual sewer system, but the Los Angeles Department of Water and Power vetoed the idea and stated that "there's a moratorium on shooting there since September 11", a position that Shiban called "understandable.
"[3] In order to make up for this, series art director Corey Kaplan was tasked with building a sewer replica on Stage 11 at the Fox studios; she used the blueprints from the 1952 version of Les Misérables as an inspiration.
[9] 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 three-and-a-half stars out of five, and called the entry "solid and efficient".
[10] The two complimented Shiban's directorial efforts, noting that "as a director [he] makes 'Underneath' shine", but were critical of some of the "trademark X-File moments", citing "the surprise appearance of a face in the bathroom mirror" and "the climactic fight in a sewer" as examples.
Crang, in his book Denying the Truth: Revisiting The X-Files after 9/11, wrote that the episode felt "very familiar" but was impressed with the production design on the sewer set.