"731" is the tenth episode of the third season of the American science fiction television series The X-Files. It premiered on the Fox network on . It was directed by Rob Bowman, and written by Frank Spotnitz. "731" featured guest appearances by Stephen McHattie, Steven Williams and Don S. Williams. The episode helps explore the series' overarching mythology. "731" earned a Nielsen household rating of 12, being watched by 17.68 million people in its initial broadcast. 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 episode, Mulder risks his life infiltrating a train carrying a human-alien hybrid. Meanwhile, Scully tries to uncover the truth about her abduction. "731" is the second half of a two-part episode, continuing the plot from the previous episode, "Nisei". The production of "731" involved several stunts, including the explosion of a retired railway car. The episode's production was successful for two members of the crew—earning director of photography John Bartley an American Society of Cinematographers award nomination for his work, and securing Bowman the job of directing the series' subsequent film adaptation, The X-Files. Plot In Perkey, West Virginia, a group of US Army soldiers arrives at an abandoned leprosy research compound, seizing most of the patients. One patient, Escalante, hides beneath a trapdoor during the arrival and follows the group to a secluded field nearby. He watches as the soldiers shoot the other patients, who are all apparent alien-human hybrids, into a mass grave. Fox Mulder loses his cell phone after jumping on top of the moving train, losing contact with Dana Scully. When questioned by Scully, X tells her to analyze her implant, saying that it will give her answers about the train and her sister Melissa's murder. Meanwhile, Mulder enters the train and finds that the secret railcar is quarantined and protected by a security system. He searches for Zama, enlisting the train conductor for help. In Zama's compartment, they find hand-written journals in Japanese. However, elsewhere on the train, the Red-Haired Man intercepts and strangles Zama. Scully sees Pendrell, who tells her that the implant contains highly advanced technology that can replicate the brain's memory functions and enable someone to know a person's very thoughts. The manufacturer of the chip was Zama, who created the implant at the West Virginia compound. Scully