The Clouds of Witness — Dorothy L. Sayers

Rustic old Riddlesdale Lodge was a Wimsey family retreat filled with country pleasures and the thrill of the hunt--until the game turned up human and quite dead. He lay among the chrysanthemums, wore slippers and a dinner jacket, and was Lord Peter's brother-in-law-to-be. His accused murderer was Wimsey's own brother, and if murder set all in the family wasn't enough to boggle the unflappable Lord Wimsey, perhaps a few twists of fate would be--a mysterious vanishing midnight letter from Egypt ... a grieving fiancee with suitcase in hand ... and a bullet destined for one very special Wimsey.