Twilight finds a mysterious file in the police archive pertaining to Sunset Shimmer and suddenly, the mystery of her missing duplicate in the human world becomes clearer.

Starlight and Trixie have long been great and powerful friends, but when that bond of friendship turns into something deeper in Starlight's heart, she feels their friendship is at stake, and fears what will come if she takes the first step.

After the return of the Pillars, an old ally of Equestria calls for new arrangements to preserve peace among the species, but is that their real intention?