Cast out of the Celestial Palace, the former Royal Student, Sunset Shimmer, is about to take life into her own hooves and seize what rightfully belongs to her, on the other side of that mysterious Mirror Portal.
Only problem is, somepony else got to the mirror, first. It's gone, vanished.
So is Celestia.
On the bright side, the new Acting Princess, Mi Amore Cadenza (or Cadance, as she likes to be called), is willing to ignore that banishment and give Sunset a second chance. She's heard the rumors about the reclusive, disobedient, and just-generally-mean Royal Student, but the Acting Princess needs all the help she can get.
So, all of a sudden, Sunset goes from being a disgraced scholar, banned from the palace grounds, to serving as a valuable asset of Princess Cadance's desperate scramble to hold the Principality of Equestria together and figure out what on Equus even happened to the Princess of the Sun.
Now, Sunset just has to avoid royally peeving off the ponies giving her a second chance: to ingratiate herself to them, even; to make herself indispensable. She can lie, cheat, and swindle like nopony else in the Celestial Palace, and it's time she used those talents for somepony other than herself.
Starting with this little project of Cadance's. The Princess needs to recruit a young group of friends to serve the Crown and Harmony, and she's already got a lead. Sunset just has to do the actual hoofwork of meeting the candidates, and then she can dust her hooves of this and go back to her studies, secure in her appointment as Royal Student.
What's the worst that could happen?
Comes after Stay of Execution, but that work is not required to appreciate this one. Provides context for Understudy.
Rated Teen for coarse horse language and various threats made to ponies' well-being.