Anadiplosis (or Helia Potter and the Other-One-Who-Lived)

Helia had been having a holiday when she was informed that the Higher Entities would like it very much if she could join an alternate universe. They informed her she would have a twin brother. She could have refused, but it sounded interesting. "Accompany Harry Potter," They said. "It'll be fulfilling," They said. But there was one thing they did not say.