 During the show's fourth season, episode co-writer Howard Gordon was slated to pen only one episode, the nineteenth entry "Synchrony".However, after hearing rumors about American CIA agents left behind during the Vietnam War, he started to develop what would become the story for "Unrequited".The day before the show's 1996 Christmas break, Howard approached series creator Chris Carter and co-executive producer Frank Spotnitz and told them about his new episode idea.