Taking place in a time period where canon fillies and colts are now mares and stallions, Princess Celestia seeks the truth about a mysterious vigilante that has recently been gaining a reputation in Canterlot after Rarity is sentenced to prison for breaking into and robbing a gem mine inside the Canterlot Mountain. Rarity refuses that she did, but evidence left by the local vigilante clearly proves otherwise. However, Sweetie Belle, recently established musician, thinks otherwise. With Celestia's help and the reformed Cutie Mark Crusaders, they attempt to solve this mystery and find out what really is going on.