After series creator Chris Carter and Howard Gordon completed the script for "Unrequited", the former assigned the latter to develop a new episode with David Greenwalt, who was new to the show and had been hired a few months prior as a producer. Gordon and Greenwalt met up and began writing what would become "Synchrony". During this process, they struggled to find a good plot, and they almost submitted a story involving an inmate swapping bodies with another man to escape prison. However, Gordon was unsatisfied with this storyline, as he believed it to be far too derivative of his previous episode. Eventually, the duo read an article in "Scientific American" about time travel: the article claimed that while classical physics does not allow for temporal displacement, quantum physics does. Gordon and Greenwalt were intrigued by the concept and decided to re-situate their episode around a related premise.