Twilight Sparkle feels sad and betrayed by her friends, Spike, brother and mentor after they have ignored the warnings that Cadence was evil. Nightmare, feel these negative feelings in the unicorn and see an opportunity.
This day could've been just perfect, the kind of day of which I've dreamt since I was small. But from too many betrayers, screwups, disgraces, and failures. Now the wedding bells will never ring at all.
Everypony likes to remember how happily the wedding ended. But what if they weren't so lucky? What would the future of Equestria be like if things hadn't worked out during that time?
Following the Changeling Invasion of Canterlot, Twilight's friends, Princess Celestia and Shining Armor lament over how they failed to protect Canterlot from the Changelings as well for their behavior towards Twilight at the Wedding Rehearsal.
After feeling unwanted and abandoned during the Canterlot Wedding, Twilight leaves to try and make a new start for her only to fall prey to a gang. Now Twilight tries to rebuild a life with no memories of her past until circumstances guide her home.
After the Changelings have been defeated, Twilight finds herself feeling lost and alone. Some study time in the library provides her the perfect solution, as she learns of the creation of the Elements of Harmony.