Three months after her tuba solo performance, Applejack receives a request letter from the new-coming polka band called the Polka Pack who are looking for an experienced sousaphone player. Seems like they've heard that she has that much of experience, just enough for her to join them because of her tuba solo performance they attended. But what about the Rainbooms and the Brass Beauties? She can still be in them can't she? Her friends accuse her for ditching them but they warn her about the Polka Pack being evil and fake. She surely doesn't want to betray her friends, but she thinks that they're just overreacting and misjudging the Polka Pack. Then she doesn't know whether to believe them or not. Are the Polka Pack truly good real people or fake evil shape shifting creatures?