Poe specified that a short story should achieve a single effect. This could be created by the overall tone and mood or by a surprise ending. He did not, of course, say anything about motion pictures, nor did he suggest that stage plays should aim for a single effect. He probably would have said that a play cannot produce a single effect because it is not short; it is broken up into acts and usually interrupted by an intermission. He was only talking about short stories. It is a waste of time looking for single effects in other literary works. Each genre has its own rationale.

It would be hard to think of movies that achieve a single effect. The best example I can think of is Citizen Kane. The reporter tries throughout the film to find out what Kane meant by saying "Rosebud" as he was dying. At the end it looks as if we in the audience are never going to find out--and then the workman throws the sled in the furnace and we see the word "Rosebud" painted on it. We realize that it symbolizes Kane's boyhood happiness when he had his mother's love. That effect is a good example of what Poe was thinking of with regard to short stories.

Another example is Alfred Hitchcock's Psycho. We don't discover until the very end that it is the son and not his mother who is the homocidal maniac and that his mother has been dead for years! However, there are other effects within the story, most notably that scene in which the naked woman is murdered with a big knife while taking a shower.