Lyra Heartstrings is a unicorn who lives in Ponyville. When Twilight Sparkle invites her to her castle, Lyra is thrilled. But soon, she gets lost on her way to the throne room! When she discovers a door that leads into a room with a giant purple mirror, Lyra's curiosity gets the best of her and she jumps in... only to find herself in a strange new world full of two-legged animals. When she realizes that everybody here is also in Equestria- pony form, of course- she sets out to find somebody that can help her return to Twilight's castle and get back to Equestria.