Gilda and Scootaloo are suspicious of their friend Rainbow Dash acting differently during her and Soarin's wedding preparations. They soon discover something every creature else did not know: Lightning Dust had finally returned and is impersonating Rainbow the whole time as revenge for the reckless pegasus' fate the last time they saw each other in 'The Washouts'.
The incomplete fan fiction that motivated this story's creation was written by Skullkittenz the Reaper on fan fiction. I made a few twitches such as getting Gilda involved and making Lightning the antagonist instead of Spitfire, since making good characters look bad is something I will never do. Plus, Spitfire may have shown some bad values before in 'Rainbow Falls' where she reveals her selfishness when she dumped Soarin for a better flyer, and was willing to take away someone else's need for her own desires, alongside Fleetfoot, dishonesty when she deceived Soarin and Rainbow into believing her lies so she could get what she wanted, and immorality when she did what was obviously wrong, but she is not immoral to the point of being evil as a villain.