A subplot is a secondary storyline in a novel or play that runs alongside the main plot, often following supporting characters, and adds depth, contrast or pressure to the central story.
Where the term comes from
Merriam-Webster defines a subplot as a subordinate plot in fiction or drama, and the word is simply sub, meaning under, joined to plot. The Wikipedia article on subplots calls it a strand of the plot that supports a side story for the main story. It says subplots may connect to the main plot in time and place or in thematic significance, that they often involve supporting characters, those besides the protagonist or antagonist, and that they may intertwine with the main plot at some point in the story. So a subplot is part of a book's design, never a separate book.
An example
In a detective novel, Inspector Aurelio Hanks hunts a poisoner in a seaside town. A subplot follows his young assistant, Neve Burrow, who is quietly helping her mother hide a debt to the very family under suspicion. For a time the two threads look separate. Then Neve's secret makes her hesitate at a key moment, and the case slips. The subplot adds a second kind of pressure, shows another side of the town and pays off in the main story.
Common mistakes
- Adding a subplot that never meets the main plot, so the reader wonders why they are reading it.
- Letting it overtake the main story in length or intensity.
- Dropping it halfway, with no resolution.
- Resolving it at the wrong time, so that it steals the climax.
- Making every secondary character carry a subplot, which blurs the focus.
How to check your manuscript
List each subplot with one line on the question it asks and one line on how it touches the main story. If you cannot write the second line, it may be a detour. Mark where each subplot appears, and make sure it surfaces regularly enough that readers remember it but sparingly enough that the main plot leads. Then find where each is resolved, ideally just before or inside the main climax. The story structure guide covers how threads weave across acts, and the romance novel guide shows how a love story can run as a subplot.
In Musael, the plan board can be filtered to show one character's thread, which makes it easy to read a subplot in order and see where it touches everything else.