Twilight never became an alicorn princess and instead lost her life as a result of Star-Swirl the Bearded's unpredictable spell. But being dead doesn't prevent Twilight from visiting those she cares for...
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.