 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 " Sanguinarium " , bizarre murders in a hospital 's plastic surgery unit lead Mulder and Scully to suspect a supernatural force may be responsible . As the uncontrolled killings continue , Mulder discovers a link between the victims ' dates of birth and key dates on the witchcraft calendar . 
