Lyra meets a few strange figures in Ponyville: some stallions & mares all dressed in black suits who ask her how she knows humans. After her interview, she follows them and find out she's discovered a secret group of ponies the not even Celestia knows. They're the Mares in Black: protecting Equestria from other dimensional creatures that aren't even a part of Equestria with technology that isn't even known. She has 2 choices: Join the Mares in Black & Protect their world from unknown dangers or have her memory erased & go back to her normal life.