Once you complete the story up to the point where you get your own house and fix it up, there will be a book and that will start the Halloween story.
after you complete the dates with Naira and Tara, the scenes with Mary, and the "potion brewing" with Sammy, then Helena will give you a house. Then you need to get 100 shells to pay for the repairs and the house is yours. The house itself is brown and located to the right of the statue in front of the path to the castle