eyes show he is now infected with the black oil. Production Conception and writing Conception of the episode originated in two visual images series creator Chris Carter had wanted to include in a script "since the beginning of the show". The first of these was that of a deep-sea diver finding a still-living pilot trapped in the wreckage of a World War II-era fighter plane; and the second was that of a black-and-white flashback taking place in a submarine. Director Rob Bowman shared with Carter his experiences diving, feeling that an episode based on finding "something creepy" underwater would be a good idea. Carter also wanted the episode to feature the re-emergence of the "MJ documents" last seen in the earlier "Paper Clip". Frank Spotnitz began working on the episode immediately after writing the earlier third-season episode "731", fleshing out the rest of the concept while on a flight out of Minneapolis. Spotnitz ended up writing his ideas on a magazine, not having brought paper with him, and included in his outline the investigation of Scully's sister's murder and the reintroduction of Alex Krycek. The title of the episode is a reference to the first and middle name of Gillian Anderson's daughter, who had been born during the production of the second season. The name Gauthier, used for the French diver and his wife, was a reference to special effects producer David Gauthier. Filming and post-production The episode's cold open was filmed in a water tank, using a replica P-51 Mustang plane which had been designed by the art director. Bowman also needed to direct a scene in which Gillian Anderson would react to a memory of playing with her sister as a child; the scene involved digitally compositing the children playing into Anderson's footage. Bowman asked Anderson to act towards a tree as though it were her sister, later telling her "I'm going to tell everybody I can that you just did that great reaction to a tree". Bowman also reshot the episode's ending, as originally Duchovny and Lea were to walk past the camera and continue off-screen. Feeling this was not effective, he replaced this with a walking shot which continued straight towards and into the camera, noting that "Nick will jump in front of a truck if he think it will make a scene better". The on-screen appearances of the black oil were achieved through visual effects,