In Part 4 of this short series, I mentioned that plot twists must be realistic. It follows logically that all of the plot must be believable, even fantasies and science fiction.
Granted, readers begin a novel understanding that what they are reading didn’t actually happen. They are ready to accept the concept of pretend. Within a fairly short period of time, however, the novelist establishes a story world with certain rules, and readers accept these and expect them to be consistent throughout.
Hence, J. R. R. Tolkien could create Hobbits, and readers accept them and understand them and expect them to behave in certain ways—the ways the author has dictated. The story, consequently would not have been believable if Frodo turned into a dragon whereas it was completely believable when he became invisible by slipping on the One True Ring.
Even contemporary stories or historicals can lose the sense of believability if they do not adhere to their own story rules. Not too long ago I read a story that supposedly took place during World War I. Never mind that the author actually called it World War I at one point, the real problem was that the segment taking place in a part of the British empire did not show the characters or the setting affected by the war apart from the fact that three individuals went off to foreign places.
No rationing. No shortages. No explanation as to why some men didn’t go to war. No mood of despair or war weariness or hope when America joined in or … you get the idea. Life seemed unaffected by a five year war! That stretches a story to the point of unbelievability.