From Citizendium, the Citizens' Compendium
The X-Files was a U.S. science-fiction television series which ran from 1993 to 2002 and also spawned two movies, as part of an extensive franchise. Created by Chris Carter, the series followed FBI agents who investigated UFO-related, supernatural and other strange phenomena. The principal cast was headed David Duchovny and Gillian Anderson as Fox Mulder and Dana Scully, with Mulder as a 'believer' in extreme possibilities and Scully a skeptic. The episodes were divided between stand-alone stories, which often featured strange and dangerous people or creatures, and instalments in a "mythology" story arc which gradually built up around a conspiracy to keep the existence of aliens out of the public domain.