High Quality Content by WIKIPEDIA articles! "Bad Blood" is the twelfth episode of the fifth season of the American science fiction television series The X-Files. Written by Vince Gilligan and directed by Cliff Bole, it aired in the United States on February 22, 1998 on the Fox network. 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 this "monster of the week" episode, Mulder and Scully must report to their supervisor, Assistant Director Walter Skinner (Mitch Pileggi) after Mulder kills a young man he believes to be a vampire. They realize that they have very different memories of the investigation.