Robert Westall 
Ghost Abbey [EPUB ebook] 

'Ninety-eight keys, none of them labelled. Ninety-eight keys, and they say there are ninety-nine rooms . . . What will you find in the ninety-ninth room, I wonder?’Maggi is delighted when her father takes a new job, renovating a crumbling stately home in Cheshire. It’s a chance to escape from the North-East, from the predatory Doris Streeton, and perhaps from the grief at the heart of Maggi’s family. But Maggi gradually comes to realize that their new home holds secrets far more sinister than anything they have left behind . . .