Hand in Glove

One of Ngaio Marsh's most ingenious novels.
The April Fool's Day had been a roaring success for all, it seemed - except for poor Mr. Cartell who had ended up in the ditch - forever.
Then there was the case of Mr. Percival Pyke Period's letter of condolence, sent before the body was found - not to mention the family squabbles.
It was a puzzling crime for Superintendent Alleyn...