 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 . 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 . 
 The show <a href='uninflect' title='1'><mark>centers</mark></a> on FBI special agents <a href='null_relcl' title='2'><mark>who</mark></a>work on cases linked to the paranormal , called X @-@ Files ; this season <a href='uninflect' title='3'><mark>focuses</mark></a> on the investigations of John Doggett ( Robert Patrick ) , Monica Reyes ( Annabeth Gish ) , and Dana Scully ( Gillian Anderson ) . In this episode , Doggett <a href='drop_aux' title='4'><mark>is</mark></a>determined to find an error in the DNA evidence <a href='null_relcl' title='5'><mark>that</mark></a>freed the convicted Robert Fassl , the " Screwdriver Killer " , whom he nearly caught in the act 13 years earlier . In the end , it is revealed that Fassl <a href='got' title='6'><mark>has</mark></a> a mental condition <a href='null_relcl' title='7'><mark>that</mark></a><a href='uninflect' title='8'><mark>splits</mark></a> him into two parts : the religious innocent and the vengeful killer . 
Da show center on FBI special agents work on cases linked to the paranormal , called X @-@ Files ; dis season focus on the investigations of John Doggett ( Robert Patrick ) , Monica Reyes ( Annabeth Gish ) , and Dana Scully ( Gillian Anderson ) . In this episode , Doggett determined to find an error in tdaDNA evidence freed the convicted Robert Fassl , the " Screwdriver Killer " , whom he nearly caught in thdact 13 years earlier . In the end , it is revealed that Fassl got a mental condition split him into two parts : thedaligious innocent and the vengeful killer .