Muriel Spark 
The Takeover [EPUB ebook] 

In the cool, historic sanctuary of Nemi rests the spirit of Diana, the Benevolent-Malign Goddess whose priests once stalked the sacred grove. Now Hubert Mallindaine, self-styled descendent of the Italian huntress, has claimed spiritual rights to a villa at Nemi – a villa with a view to kill. But his protector, the indestructible millionaire Maggie Radcliffe, has withdrawn her patronage – and the supplicant sets out to appease his ancestress. With gruesome results . . .