The X-Files - Season 4 Episode 6 Sanguinarium The truth is out there.
Overview: After a doctor loses control and kills a patient on the operating table, Scully hypothesizes that it's linked to work-related stress, while Mulder is convinced of a more sinister reason. After he finds a link between the victim and the four witches Sabbaths, he suspects that a nurse may be practicing witchcraft.