Rarely will any story consist of a single story. Most likely, the hero will be pursing the main story while multiple other minor characters (including the villain) are busy pursuing their own goals in their own stories. The first big mistake novices make is not using subplots that mirror the main story. The second biggest mistake novices make is not converging the subplots with the main story at the end.
One of the best flawed movies to study is “Inglorious Basterds,” which starts off introducing a sadistic Jew Hunter who orders his soldiers to machine gun a Jewish family hiding underneath a house. Out of the entire family, only the French girl survives so right away the story seems to set up a show down between this French girl and the Jew Hunter. Suddenly, the story introduces us to a Jewish commando unit known as the Inglorious Basterds. Their job is to live behind enemy lines and kill Nazis.
Where “Inglorious Basterds” makes a mistake is that the story between the French girl and the Jew Hunter never really combines with the story between the Inglorious Basterds and the Jew Hunter. They all converge in the movie theater, but the French girl gets killed by a German soldier. Then the Inglorious Basterds get captured by the Jew Hunter, who inexplicably lets them free in exchange for letting him escape to the American side.
First, the Jew Hunter’s desire to escape to the American side is never set up so his desire to do so comes out of nowhere, and his capture of the Inglorious Basterds seems like a horrible situation, but then he willingly arms them and puts himself at their mercy to escape the Nazis. That’s a flawed ending.
Look at “Star Wars” to see how subplots converge. First, we’re introduced to the main subplot where Darth Vader is trying to get the stolen Death Star plans from Princess Leia. Then Luke is trying to find Princess Leia, so the one item that can force these stories to converge is Princess Leia, and that’s exactly what happens. Darth Vader is still trying to get Princess Leia in the end by blowing up the rebel base, while Luke is trying to stop the Death Star in the process. When Luke wins, that completes the story between Darth Vader and Princess Leia at the same time.
In comparison, “Inglorious Basterds” never completes the French girl’s conflict with the Jew Hunter and when the French girl’s story does end, it ends before the story with the Inglorious Basterds, so the outcome isn’t unified because the stories don’t converge like in “Star Wars.”
Study any good movie and you’ll see that the climax is where everything gets resolved at once while in “Inglorious Basterds,” the different stories get resolved separately one after another, which makes for a less satisfying climax.
Resolve your separate stories as close together as possible and make sure they converge together somehow. In “Star Wars,” Princess Leia represents the common denominator that unites Luke and Darth Vader. In “Inglorious Basterds,” the common denominator should have been the Jew Hunter, but it isn’t, and that’s why “Inglorious Basterds” ends on a less than perfect note.