Fluttershy has a feeling, a really bad feeling. That this year's Summer Sun Celebration, won't turn out to be a blast. She was right, the worst of all villians, appeared at her house the day before. Her twin sister. Fluttershy thought she could get away, but her sister found her again. She has to find a way to tell her friends about the fact that her sister wants them dead. And she better do it quickly, before everypony in Equestria is running away from a deadly murderer.