A. E. W. Mason 
Four Corners Of The World 

When Archie Cranfield’s father asked Mr. Twiss to look after his son as well as advise him financially, the solicitor had no idea what he was agreeing to. A furtive smile permanently etched on his face, Archie lives alone in the countryside. His neighbors do not like him, and Captain Brayton, a former schoolmate, had a falling-out with him years ago and has not seen him since. Then the oddest surprise of all-Archie invites Brayton for a weekend visit and the captain winds up dead. Is it suicide, or is the young Mr. Cranfield as guilty as he looks? (Goodreads)