Twilight Sparkle's tenure in Ponyville has been anything but calm. Since the Summer Sun celebration, she's dealt with a variety of foes, from Nightmare Moon to dragons, hydras, Discord, and King Sombra. But when Pinkie Pie asks for help with a small problem, Twilight finds herself pulling out all the stops to deal with the most dastardly (and curious) fiend yet encountered: Sugarcube Corner’s haunted mailbox. Rainbow Dash’s letter from the Wonderbolt Academy is on the line. Failure is not an option.