A Malignant House — Fay Sampson

Suzie Fewings, a keen family history researcher, is delighted to be given access to a chest of old documents at the local stately home, Hereward Court. She tries to ignore disturbing rumours about the owner, Floridus Hereward, but when she's threatened by a sinister visitor to the house, the police are bafflingly unhelpful . . .