 = Underneath ( The X @-@ Files ) = 
 
 " Underneath " is the twelfth episode of the ninth season of the American science fiction television series The X @-@ Files . The episode first aired in the United States on March 31 , 2002 on the Fox network . The episode was written and directed by executive producer John Shiban . The episode is a " monster @-@ of @-@ the @-@ week " episode , a stand @-@ alone plot which is unconnected to the mythology , or overarching fictional history , of The X @-@ Files . The episode earned a Nielsen rating of 4 @.@ 4 and was viewed by 4 @.@ 64 million households and 7 @.@ 3 million viewers . It received mixed reviews from critics . 
 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 ( <unk> <unk> ) , 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 " <unk> Killer " , whom he nearly caught in the act 13 years earlier . In the end , it is revealed that Fassl has a mental condition that splits him into two parts : the religious innocent and the vengeful killer . 
 " Underneath " marked the directorial debut of Shiban , who had been a writer for the series for several seasons . Reportedly , the episode contained " so many problems " that the Fox executives nearly refused to allow the finished product to air . At the last minute , however , they relented , and allowed the episode to be aired later on in the season , several weeks after its intended air date . Shiban originally wanted to film the sewer scenes in Los Angeles ' actual sewer system , but due to the events of September 11 , a sewer mock @-@ up was built on Stage 11 at the Fox studios . 
 
 = = Plot = = 
 
 Thirteen years before the present , Robert Fassl ( W. Earl Brown ) sits in his van . He later approaches a home and claims to be there to repair the cable . As Fassl holds up a piece of paper to show it to the family who called for the repair , blood <unk> splashes across the paper . He looks up and sees the house 's occupants with slit <unk> in pools of blood . <unk> , two police officers burst into the house and apprehend Fassl . One of the officers who goes to check out the kitchen , turns to reveal he is John Doggett ( Robert Patrick ) as a young <unk> officer . 
 In the present , Monica Reyes ( <unk> <unk> ) discusses Fassl 's release — due to DNA evidence — with an outraged Doggett . Dana Scully ( Gillian Anderson ) confirms that the test results conclusively <unk> Fassl as the killer . Meanwhile , in court , Fassl notices a mysterious Bearded Man . After being released , he stays in a room belonging to his lawyer , Jana Fain , where he clutches a <unk> beads and prays frantically . When the Bearded Man appears , Fassl begs for the man not to hurt her . While Fain is unharmed , Fassl learns that the housekeeper , Mrs. <unk> , has gone missing . Fassl finds her body , <unk> up the blood , and <unk> her remains to cover up what has happened . 
 Scully tells Doggett that while the DNA test <unk> Fassl 's <unk> , it <unk> a possible blood relative ; Fassl , however , is an only child . Reyes proposes that the murders are being conducted by an entity rather than a person . Meanwhile , Fassl approaches Assistant District Attorney Damon Kaylor and begs to be sent back to prison . Kaylor refuses , but is killed by the Bearded Man . After hearing of Kaylor 's disappearance , Reyes <unk> that Fassl 's piety and his unwillingness to acknowledge his darker half has given him the <unk> ability to physically change into another , more violent person . 
 The Bearded Man demands that Fassl kill Fain , beating him up when he doesn 't comply . As she tends to Fassl , Fain first sees the Bearded Man in his place . While <unk> out Fain 's house , the agents see the Bearded Man flee . Doggett pursues the Bearded Man while Reyes finds Fain alive . In the pursuit , Reyes falls through into a sewer , where she finds the remains of the Bearded Man 's victims . After a struggle with the Bearded Man , Doggett ends up <unk> Fassl , much to his confusion . Reyes tries to remind him that it does not matter as long as the case is solved . 
 
 = = Production = = 
 
 " Underneath " was written and directed by executive producer John Shiban . This marked his directorial debut . According to Shiban , part of the inspiration for the episode was that 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 . Another inspiration for the episode was the 1949 film The Third Man , which featured a climactic chase through a sewage system . 
 The episode , which explores John Doggett 's backstory as a New York City police officer , was described as containing similar themes as those " explored on the Millennium series . " The episode guest @-@ starred Arthur Nascarella , who was a friend of series co @-@ star Robert Patrick . Patrick was essential in getting Nascarella cast on the show ; he later joked " I stole [ Nascarella 's ] New York accent in Copland [ sic ] and I stole it to do The X @-@ Files , but I got him cast in The X @-@ Files show . " 
 As the ninth season progressed and the show 's ratings began to <unk> , Fox became more and more actively involved in the show 's style and direction . Although " Underneath " was the twelfth episode aired , it was actually the ninth episode produced during the season ; reportedly , the episode contained " so many problems " that the Fox executives very nearly <unk> the finished product . At the last minute , however , they relented , and allowed the episode to be aired later on in the season , several weeks after its intended air date . 
 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 . " In order to make up for this , series art director Corey Kaplan was tasked with building a sewer replica ; she used the blueprints from the 1952 version of Les <unk> as an inspiration . Eventually , a complete set was built on Stage 11 at the Fox studios . 
 
 = = Reception = = 
 
 " Underneath " first aired in the United States on March 31 , 2002 on the Fox network . The episode later debuted in the United Kingdom on February 2 , 2003 on BBC One . The episode earned a Nielsen household rating of 4 @.@ 4 , meaning that it was seen by 4 @.@ 4 % of the nation 's estimated households and was viewed by 4 @.@ 64 million households and over 7 @.@ 3 million viewers . " Underneath " was the <unk> most watched episode of television that aired during the week ending March 31 . 
 The episode received mixed reviews from television critics . Jessica Morgan from Television Without Pity gave the episode a B – rating . John Keegan from Critical Myth gave the episode a negative review and called it " easily the worst of the season " . He awarded it a 4 out of 10 and concluded that , " We can only hope that none of the remaining episodes are Shiban @-@ related , and pray that he can do a much better job when he writes for Enterprise next season . " 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 " . 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 . Shearman and Pearson , however , wrote positively of Shiban 's realistic depiction of Doggett . <unk> <unk> , in his book <unk> the Truth : <unk> The X @-@ Files after 9 / 11 , wrote that the episode felt " very familiar " but was impressed with the production design on the sewer set . 
 
 