A. E. W. Mason 
The House of the Arrow 

When Boris Waberski, brother-in-law of the wealthy widow Mrs. Harlowe, attempts to talk her English solicitors into advancing him money on his expectations as her heir, he is ignored. Unknown to Waberski, he has been disinherited in favour of Betty Harlowe, the niece of Mrs. Harlowe’s late husband. But when Mrs. Harlowe dies suddenly and Waberski accuses Betty of murder, junior partner Jim Frobisher is sent to the estate to find out what’s really going on.