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First broadcast December 1, 1995, "731" was the conclusion of a two-part X-Files story that began with the previous week's "Nisei." While trying to confirm the authenticity of an "alien autopsy" videotape, Mulder and Scully have stumbled upon an international conspiracy involving a group of Japanese scientists. In addition, Scully is provided with clues pertaining to her mysterious disappearance of the previous year. Unfortunately, neither agent may live long enough to reveal the truth -- Mulder is stuck on board a booby-trapped train, and Scully is forced to deal with a shadowy government figure who might turn out to be her assassin. Both "Nisei" and "731" were written by Chris Carter, Howard Gordon, and Frank Spotnitz.