Accompanying an architect in an examination of the faded ancestral pile of Cranbury Hall, prim solicitor Arthur Gilroy happens upon his wastrel half brother Oliver, with whom he has an interview later that evening, who is rather elliptical about the reason for his presence. The two part on not unfriendly terms and, soon after, a shot rings out that is attributed to poachers taking liberties on the ownerless land. But when Oliver fails to show up for their meeting, Arthur begins to suspect that “some mysterious tragedy had occurred”…and he might be right, since that shot turns out to have been merely the first attempt on Oliver’s life.
I was pretty much goaded into this, you should know. Ben at The Green Capsule is diversifying his blogging to extend beyond the works of John Dickson Carr, and the first book he chose was 
Summoned by a distant relative to a secluded family pile, a young(ish) man finds himself isolated with a fixed cast of closely-related characters as money-hungry relatives, murder, and all other sorts of puzzle plotting chicanery inveigle themself onto the scene. Yes, in many ways No Flowers By Request takes the exact same ingredients as 
The Invisible Event 