I’m planning my new novel (as much as a pantster can) and have been thinking a lot about subplots. I love dreaming them up - B stories, those side stories that add dimension and complexity to the main narrative. Take a suspense thriller for example. Our heroine Susan, is a teacher. An outbreak of bizarre behaviour among her high school students leads her to believe they are being mysteriously hypnotised. Solving the puzzle is the main plot. But perhaps Susan also has trouble at home, a rocky marriage she’s trying to save. We’ll see a different side of her in scenes where she fighting for her relationship, than we will when she’s being a super sleuth. Subplots allow writers to deepen characterisation.
Used well, subplots also help emphasise theme. The theme may be finding one’s authentic self. In the main story, Susan’s exploration of hypnosis and the human psyche makes her question her mundane, unadventurous life. Is it fulfilling or has she settled? In the subplot, Susan holds on to her husband, by pretending to be someone she’s not. At some point she realises she needs to let him go. The subplot illustrates theme from a different angle.
Subplots give readers variety - a rest from the main plot, especially if you’ve hit a slow patch. You can switch over to an interesting subplot and let the main story play out in the background for a bit. They can provide light relief, an opportunity for humour to be injected into a serious story. And they can be a lot of fun to write. Remember though, they should be tackled in the same way as your main plot with their own narrative arc. And they shouldn’t overwhelm the story. If a subplot takes over the main one, it’s trying to tell you something. Maybe that’s where the action really is?