After Pony Magazine declares Twilight Sparkle to be the most eligible bachelorette in all of Equestria, Twilight's friends help her sort through the flowers and love letters sent to her by ponies all across Equestria.
One day, Twilight Sparkle discovers something amazing about her friend Sunset Shimmer. She's a magical talking pony! This requires investigation! Science! Possibly a full-body physical! Or maybe she'll just ask her what's up with that.
Sunset Shimmer invites Twilight over to spend the night at her home in the wake of the Friendship Games fiasco, and Twilight learns that they have a lot more in common than she expected.
A murder in the mirror world brings Sunset Shimmer back to Equestria, with her world's Twilight Sparkle in tow. While they track the killer, they struggle to reconcile the differences between them and their mirror counterparts.
A tale in the Berylverse. Meanwhile, a reality away, Sunset Shimmer's life has changed since she met Princess Twilight...and it's about to change even more, whether she likes it or not.