Twilight Sparkle finds herself being led to question things she's never questioned and try things she'd never tried by Rarity. But slowly Twilight begins to feel like she's being corrupted, and begins to wonder if Rarity is a vampire.
Shortly before the return of Nightmare Moon, her daughter wants nothing more than to have Equestria fall into eternal night and Celestia ousted. However, when she meets a young batpony her plans for revenge will be put on hold.