A subplot is a minor story within a larger work. It exists to give the main plot more depth.

1. The subplot must affect the hero’s main plot, or it shouldn’t be there at all. If the subplot doesn’t serve the main plot, you have two simultaneous stories that may be clinically interesting to the audience, but they make the main plot seem too long. To connect the subplot to the main plot, make sure the two dovetail neatly, usually near the end.

2. The subplot character is usually not the ally. The subplot character and the ally have two separate functions in the story. The ally helps the hero in the main plot. The subplot character drives a different but related plot that you compare to the main plot. Most Hollywood movies today have multiple genres, but they rarely have true subplots. A subplot extends the story, and most Hollywood films are too interested in speed to put up with that. Where we see true subplots most often is in love stories, which is a form that tends to have a thin main plot.

To Subplot Or Not To Subplot?

Benefits
  • Improves character, theme and texture of story.
  • In a dark story, a subplot can lighten the mood (or vice versa).
  • A subplot can serve to make it more difficult for the main character to reach their goal.
Downside

Decide whether the texture of the story or the speed is more important.

Because the subplot exists to expand on the theme and character, you may need to write a first draft of your main story before realising the sort of story that would make for a good subplot. In other words, if the subplot exists to expand upon the theme, the theme must first reveal itself.

Alternative Opinion: Subplot Is Not A Useful Concept

‘Subplot’ is a misnomer. A good one that works is actually a story plot of its own with its own complete structure.

A more accurate term might be ‘side story’. But we can keep calling it ‘subplot’, because that’s what it’s widely known as.

I actually don’t even like talking about subplots. Whenever someone asks me “how do I write subplots?”, it makes me incredibly squirmy. I don’t have a good simple answer, for the simple reason that subplots are not a good way to think about story.

In fact, I recommend you stop thinking about subplots altogether. Instead, just think about plot.

K.M. Weiland

Writing Tips

If you are going to use a subplot, you only have enough time to give it the seven most basic story elements. Don’t try to get any more fancy than that. Because of the limited time you have to tell a complete subplot, introduce your subplot early. The main plot begins and ends the novel. Sub-plots should begin and end within the main plot.

Don’t stray from the main plot for too long because then you risk the story collapsing.

Lots of subplots exist to complicate the plot and make it difficult for the main character to get what they want. A particularly useful type of subplot, however, does something more than just complicate the quest. It makes the main character question what they want entirely.

Sub-plots add layers and texture to your novel, because they:

  1. Show different perspectives of the central conflict in the story
  2. Test your main characters’ motivations and abilities to achieve their goals
  3. Show different aspects of the protagonist’s personality

If your sub-plot does not do at least one of these, it will feel like a stand-alone story within your novel.

— from Writers Write

Case Studies

Pulp Fiction

Quentin Tarantino’s Pulp Fiction tells two stories. One is about how Jules comes to believe that God has a mission for him. At the Showdown, he doesn’t shoot the robber because he’s going through a “transitional period.” In the other story, Butch refuses to throw a prizefight and comes to terms with his boss while escaping with his life.

Each of the two stories has a beginning, a middle and an end, but the events are not presented in exact chronological order.

Tootsie

For a close look at the subplot in Tootsie, see The One Subplot You Really Need from Cracking Yarns