One thing I enjoy about Agatha Christie's mysteries is that often there are tiny breadcrumbs left for the reader to find which would point in the direction of the murderer. Often, as in the case of this book, I make note of certain things (like physical description) and think to myself that it will probably be important later, and then promptly forget about it only to be reminded of it at the very end when that tiny detail is used as part of the clue that shows who the real murderer is.