In a surprise meeting, Princess Celestia reveals the truth behind the friendship letters that Twilight and her friends have been writing. It seems that the maturity and stability of the Elements of Harmony were being judged, in order to determine their suitability as initiates into a secret organization with a grim purpose. Their mission is to defeat an impending "darkness" that hasn't actually been proven to exist at all. But Celestia knows it's coming, so it must be true!

But when only two of the six friends are initiated into the club, what effects will it have on the Elements' friendship? Two unsuspecting mares must adapt to a new lifestyle while still handling their mortal duties, while the remaining four ponies deal with their rejection like mature adults.