Patricia Wentworth 
Who Pays the Piper? [EPUB ebook] 

‘I always get what I want.’ Thus spoke Lucas Dale, a wealthy man in his early forties who had come to live at King’s Bourne, former family home of Susan Lennox. He means to have Susan as his wife, but she is already engaged. This does not deter him in his purpose and he resorts to trying to blackmail Susan to promise to marry him. He is murdered and suspicion falls on Susan’s fiance who was heard to threaten his life.