After seeing what happened when she accidently changed her friends destinies, Twilight is curious about about the 'what if'. Like, for example, what if Luna had ponies a thousand years ago who noticed her.
Apple Bloom was expecting to find out about the niece she never knew existed. What Applejack shares with her, a secret she held for so many years, threatens to shake Apple Bloom’s world.
When Twilight Sparkles from alternate dimensions begin popping up in Equestria, it is up to Scootaloo to round them all up and find a way to send them home and retrieve her world's Twilight.
One day, an enigmatic pony named Burke arrives in Ponyville He happens across the Cutie Mark Crusaders, and promises them their cutie marks in return for their assistance. Hijinks ensue. *Not related to Fallout Equestria*