癌人
Writers for the series often struggled with writing "mytharc" episodes because there was a need to force as much material into them as possible, given their relative paucity compared to the "Monster of the week" episodes. Originally, a large portion of the episode was supposed to reveal the history of the Syndicate via flashback. Reportedly, these scenes would have featured younger versions of Bill Mulder (played by Peter Donat), The Smoking Man, Dr. Openshaw, the Elders, and many others. However, this idea never panned out, and Carter and Spotnitz reframed the episode around narration, courtesy of the Smoking Man, whose scenes were completed under extreme pressure near the end of production. While the title of the previous episode, "Two Fathers", referred to both Bill Mulder and The Smoking Man, this episode was titled "One Son" to reflect the fact that Mulder was the only remaining son of either of these men, after the presumed death of Jeffrey Spender and the rejection of Alex Krycek.