Although stage magic doesn't seem like it would be the center of a deadly mystery, the plot of The Prestige proves otherwise. Angrier learns that Borden is a pair of identical twins performing the act. Angrier, however, is comprised of several clones of the original Angrier, who was drowned.
Murder on the Orient Express
Murder on the Orient Express is the film adaptation of an Agatha Christie novel, so of course, the audience should be expecting some sort of grand twist. The murder mystery turned out to have a killer that no one could have anticipated: everybody. Every single passenger on the Orient Express conspired to murder Edward Ratchett for a number of reasons.