Spoiler Alert: in WHAT WHODUNIT did the "who" turn out to be Hector McQueen, Edward Masterman, John Arbuthnot, Harriet Hubbard, Natalia Dragomiroff, Mary Debenham, Hildegarde Schmidt, Antonio Foscarelli, Greta Ohlsson, Pierre Michel, Cyrus Hardman, and Rudolph Andrenyi -- but not Rudolph's wife Helena?
MURDER ON THE ORIENT EXPRESS (by Agatha Christie)