When Twilight left, Sunset forgot to ask how Princess Celestia was doing. Seeing as she will not get an answer, the former student to the Solar Goddess attempts to move on and live life as a student to Princess Twilight.
One night, while Sunset drifts further into her dreams, she is visited by none other than the guardian of dreams: Princess Luna of Everfree. This will only end one way, and that way is completely opposite of what Sunset had been expecting. Takes place directly after Rainbow Rocks.