The difference between a story’s plot and its main idea is that plot organizes time and events while the main idea organizes theme. Both plot and main idea provide structure, and their functions in stories are often intertwined, depending on the genre of the story. Also, while a story generally has only one main idea, a story can contain many different plots.
Readers often confuse plot and main idea in fiction because of their willing suspension of disbelief. When readers “fall into” a story, they forget that it is a contrivance concocted by the writer to make a point (the main idea or theme). Because plot serves theme by moving characters around so that they can demonstrate the writer’s thesis, these devices can seem to be the same thing. Rather than an action or event, the main point is an abstract idea that the writer reinforces over the course of the story, such as the notion that war is evil or that sinners have to suffer. In well-written stories, plot and main point are in accordance with a literary type. The plots of romance novels, for instance, don’t match well with readers’ expectations about weighty subjects like square dealing and codes of ethics, while the plots of Westerns do.