The script for "Synchrony" took over a week to write, with some day-long sessions lasting over 15-hours. Gordon and Greenwalt were also assisted by fellow writers Ken Horton, John Shiban, and co-executive producer Frank Spotnitz. A few days before filming was slated to begin, Gordon was still frantically reworking the teleplay; during these last-minute rewrites, he removed a number of elements, including two "useless characters" (one of whom was a Stephen Hawking-esque scientist in a wheelchair)a move that he claims "really tightened up the story". David Duchovny later revealed that a few of the episode's scenes were even written during filming "because no one could know if the audience understood what was happening". Gordon later said, "In the end, I think it worked, but it's getting there that's really difficult." The experience proved so challenging that Gordon very nearly considered aborting the project, and after finally delivering the script, he swore off writing about time travel.