It’s take-me-to-your-leader time on General Hospital. Bored with the usual soap themes of romance and betrayal, the show’s writers have lit out for the supernatural again. (Remember the evil plot to freeze over the city of Port Charles?) The new story line concerns a visitor from the planet Lumina (Bradley Lockerman) who comes to Earth to secure a powerful crystal. Oh, please. The afternoon serials just aren’t equipped to deal with sci-fi subjects. The scale is too small and the focus too personal to make it work.