(Spoilers: Whiplash, Guardians of the Galaxy, Almost Famous, 40 Year-Old Virgin, Star Wars, Bridge of Spies, Inception)
Most discussion of screenwriting technique focuses on how to create a great A-plot for your story, but great subplots can enhance both the A-plot and the overall movie experience. The important thing is that the subplot serve some purpose to the overall story. Here are four ways to use subplots effectively.
1. A subplot can reveal character.
You can create a subplot that will demonstrate an aspect of the main character that is difficult to bring out in the main plot. For example, in Guardians of the Galaxy, (written by James Gunn and Nicole Perlman) the subplot involving Peter Quill’s mother humanizes him and makes him sympathetic. This helps us root for a character who is a self-absorbed thief when we first meet him.
And in Whiplash (written by Damien Chazelle), Andrew’s romance with Nicole illustrates aspects of his character. For example, we see the destructive nature of his commitment to his musical goals when he breaks up with Nicole simply because he anticipates she may not be supportive sometime in the future. Later, when he calls to try to reconnect, we can see that he has realized he may have had misplaced priorities.
2. A subplot can trigger character arc.
In some stories, the character needs to change in order to achieve their goal. A subplot can provide the impetus for that change. Often that comes in the form of a mentor. In Star Wars (written by George Lucas), Luke’s relationship with Obi Wan Kenobi is the trigger that starts him learning about the Force. It is this growth that ultimately allows him to destroy the Death Star in the end.
Love interests often serve this purpose as well. In Almost Famous (written by Cameron Crowe), William needs to lose his awe of the rock stars in order to become a serious journalist. His relationship with Penny Lane causes him to recognize the negative aspect of the band he worships when he sees how they treat her. This is the impetus for him to write a great article about the band.
3. A subplot can reveal different approaches to the theme.
If your main character is taking one approach to the issue of the film, you can use subplots to demonstrate other approaches. This can deepen the thematic complexity of the story and reveal the pros and cons of the main character’s approach. In Whiplash, Andrew’s father provides an example of a loving, supportive mentor relationship in comparison to the abusive relationship Andrew has with Fletcher. But Andrew’s father also shows what happens when an artist compromises and settles for mediocrity.
The subject matter of The 40 Year-Old Virgin (written by Judd Apatow & Steve Carell) is sex. Andy’s three friends have different approaches to the subject of sex. David is still obsessed with an ex-girlfriend, Cal is only interested in one-night-stands, and Jay is in an apparently happy relationship, but insists on cheating on his girlfriend. Each offers a different perspective on sex and its place in relationships, and each has a character arc that adds complexity to the subject matter of the movie.
4. A subplot can provide stakes for the main character.
If the main character in your story needs personal stakes, then a subplot can provide them. In Bridge of Spies (written by Matt Charman and Ethan & Joel Coen), the main character of James Donovan cares about the outcome of the legal case he’s defending and the subsequent prisoner exchange negotiation because he’s an ethical lawyer. This provides some stakes, but no personal downside to James’ success or failure. However, the subplot with his family gives James something to lose. By following his ethical course, he puts his family in peril, as witnessed by the shots fired through the living room window while his daughter is on the couch.
In Inception (written by Christopher Nolan), the subplot with Cobb’s family performs a similar function, and then twists it. On the surface, Cobb is determined to succeed at the mission of the film because if he does, he is promised the opportunity to reunite with his children. However, we then learn through this subplot that Cobb may actually be trapped in a dream. This provides added stakes – if it is a dream, then Cobb can only be reunited with his children by rejecting it.
Most of these are examples of dramatization, or “show, don’t tell.” Rather than have the character talk about how they feel, their backstory, or the thematic concepts of the story, you can demonstrate those ideas with a subplot. It’s more dramatic, powerful, and realistic.