Nelly and her family are in for a truly spooky weekend, having decided to visit a genuine haunted castle. At least, that’s what the newspaper advert promises. Lena-Sleva, Nelly’s old teacher, asks Nelly to try out a new invention that Uncle Hannibal has come up with. It’s a ghost detector used to search for ghosts and ghouls. Because, according to Lena-Sleva, ghosts have become very, very rare these days, and nobody really knows where they’ve gone…