Hobswyke by C. R. Clarke
The finish of school life should have gifted Lucy Claybourne an uncomplicated summer, that is, until she makes the decision to revisit Hobswyke Hall - a derelict manor house that was once her childhood home.
Half a decade has passed since Lucy and her mother abandoned the gothic monstrosity that lords over the estate that surrounds it like a spider in its web and moved into the gatehouse on the far side of the grounds, a move supposedly made as a money saving exercise. But upon reacquaintance, Lucy realises there had to be more to the move than money, and it becomes her intention to find out what?
As she spends time in the hollow of the house, surrounded by ghosts and shadows from her past, she becomes aware of something unholy residing in the bones of the old building, something that may have been left behind by the previous owner, the occultist, Antoine Mallette, who's activities have fuelled over 200 years of morbid gossip. Then the groundkeeper's son, Sam Fletcher, makes a terrifying discovery, a discovery that will alter the path of Lucy's life in ways that will make her question everything she's ever known, and anything she's ever been told by those she holds closest to her heart.
There is something very wrong with Hobswyke Hall, but some things are better off left to rot.