Season 6 Episode 6 - How the Ghosts Stole Christmas 

Mulder talks Scully into investigating a haunted house on Christmas Eve where several couples have met their fate. While there they encounter endless tricks and traps set by a ghostly couple who originally made a lovers suicide pact in the house.
Keywords: the x-files, full episode, scully, mulder, season 6, episode 6, 6x06, the ghosts who stole christmas