The dénouement is the quiet recovery scene of your book. It’s the happy celebration time when awards are bestowed and the couple get married. The main danger of the book is gone—the good, free people of the world have defeated it—and now we enter into our well-deserved time of peace.
Your reader needs this scene. She’s been through the wringer, too, and you owe her a celebration.
Just as the climactic portion of Act 3 has four components, so does the dénouement. To complete your novel you must:
1. Show the main character’s final state (the end condition after his inner journey).
2. Show the overall disposition of things now that the climax has passed.
3. Tie off all loose ends.
4. Suggest how things might be moving forward for the characters (including an indication that danger still exists, if you’re setting up a sequel).
Remember the medal ceremony at the end of Star Wars? That’s what I’m talking about. This is the time to smile again, to believe that, because of what we did here, tomorrow can be a day of hope.
Now, if your story has a dark ending, you still need to write a dénouement. Show the disposition of things now that the crisis is over. The jackboots march through the flower garden, the gibbets are busy, and the black fleet sets sail to rule with terrible might.
Either way, your reader has earned a bit of closure and tying off. Your story needs it too.