A pocket full of grain - Agatha Christie

Mr. Rex Fortescue died suddenly in his office after drinking the tea his secretary had made for him, and then found a handful of rye in his pocket.

Inspector Neil begins the search and investigation in his quiet way and collects information from the residents of the dead man's house, but he is soon surprised by the second crime that shuffles the papers!

When Miss Marple arrives some strange things start to line up in an apparent context, but Inspector Neil can hardly believe. Could Miss Marple be right?