According to Flannery O’Connor in her Mystery & Manners, meaning is “embodied” within the story, while a theme is an abstract idea, an element that’s recognizable enough to extract from the story. Meaning conveys some “mystery of existence” and can be associated with the elements that matter most to the characters. The writer must convey what matters most to himself or to his readers, not just elaborate on some abstract idea.
When I am asked what the plot is for my story, I understand that one sentence is insufficient for describing my story; I must tell it all. If my theme were easily recognizable, then the plot would be predictable. Likewise, in relation to O’Connor’s explanation, an excellent moral or plot cannot be simply stated without telling the whole story. Ultimately, the mystery of the plot must be intricate enough to grab and maintain the reader’s interest.