Princess Celestia was dead. She was found lying face down in her own room, a dagger buried in her neck. The castle guards tried to conceal it, but of course it was no use; words travel fast, whether they are right or not. To make matters worse, Princess Luna has disappeared, leaving Equestria without a ruler. However, nopony seems to know where Luna went. When word of Celestia's death comes to Ponyville, Twilight Sparkle and her friends know that they have to find out the truth, no matter where they have to go and what they might face.