STARTING SCENE: You walk up the gangplank to board the Titanic.

ENDING SCENE: You finish eating in the onboard dining room on the first night of the cruise.

Hello? Any plot here?

Your plot arc is equal to how successful your story will be. Why? Because word-of-mouth is the best advertising that any story can have, and when readers describe a book to each other, they often describe the plot arc.

The plot arc is the destination that your story takes from its starting point to its climax. This is not 'boy meets girl'; that is an incident. Nor is it 'boy meets girl, does wacky stuff to trick her into marriage, then lives happily ever after'; that tells what happened after the climax. Plot arc is: 'boy does wacky stuff to trick newly-met girl into marriage'.

From this plot arc, you can tell where the beginning of the story is and where it should end. Should you write 4 chapters describing the boy as a loser before he meets the girl? No! That would change the plot arc to: 'Loser does wacky stuff to trick newly-met girl into marriage'.

You might think that this is a subtle change, but it changes the whole story arc, the perspectives of the characters, and their attitudes; it is not the same story. But the same rule applies: from the plot arc, you should know where the story starts and what the climax is.

You want to avoid writing stories where the plot arc sounds idiotic: 'Frodo invents a transporter that teleports him to the Land of Oz where he must fight Darth Vader.' The plot arc will tell you if you should be writing the story or wondering if you are insane.

Plot arcs need not be physical activity: 'man goes camping with army buddies and all of them suffer from flashbacks to the war.' What you want to avoid is: 'man and his old buddies from the army stare into a campfire.' A good plot arc must include an action, even if it is just emotional.

Why do you need a plot arc? A plot arc can tell you things about your story that may not be obvious. Are you beginning and ending your story in the right place? Do you maintain ongoing tension? Is your story a single growing thread or a series of unrelated incidents? Are your subplots beneficial to your story?

All writers suffer from some level of tunnel-vision; we may think that a story is great, but it could be all about a character that we love, and not really have a storyline. Plot arcs give writers a perspective that we might otherwise lack.