Most stories have at least one subplot that runs alongside the main plot. Some of these run the full length of the story, some are short little side routes. For example, in the Sherlock Holmes stories the main plot is the case and the secondary plot is Holmes and Watson’s friendship and runs concurrent to the main plot. In The Avengers Assemble there’s a subplot about whether or not Bruce Banner can control The Hulk, Thor’s relationship to his brother Loki and Black Widow paying for past sins. In Pride and Prejudice Lizzie’s sister Lydia elopes, her friend Charlotte marries Mr Collins and, of course, the romance between Jane and Bingley.
Subplots can be troublesome because although they don’t have to directly relate to the main plot they can’t drift too far away from it. For instance all the subplots in Pride and Prejudice intersect with the main plot but, arguably, could exist as separate stories. At the point Wickham elopes with Lydia we know he’s a ‘Bad ‘Un’ from what we’ve learnt about him from Lizzie and Darcy’s plot. However, we could have a story that about Wickham and Lydia eloping in which Lizzie and Darcy’s involvement becomes a subplot but that story might be less interesting to the reader. This is something we have to remember when writing a subplot, it isn’t something that simply exists when it is mentioned in the main plot, it has to have sense that when it’s not on the page it’s carrying on somewhere else. It might be so interesting the reader looks forward to it reappearing or sometimes the reader might not realise that it is a subplot until it comes to fruition and they can put the pieces together.
However, we decide to work our subplot into the story it has to have a beginning and an end, as with the main plot. As with the main plot we might not have a tidy end or it may be that in resolving the main plot we also resolve the subplot. For example, in Pride and Prejudice Darcy falling in love with Lizzie helps to resolve the Jane and Bingley subplot because it changes his view of Bingley marrying Jane. The subplots also inform the events of the main plot such as Lizzie’s changing view of Wickham, who at first appears nicer than Darcy, alters her opinion of Darcy, particularly when Darcy prevents Wickham from abandoning Lydia.
So, although the subplots have to function as stories themselves they, usually, need the main plot. We might be able to make the elopement of Wickham and Lydia a main plot but we would still need the relationship between Lizzie and Darcy as a subplot to resolve the story. If Darcy hadn’t fallen in love with Lizzie he wouldn’t have intervened with Wickham and if Darcy hadn’t intervened with Wickham then Lizzie wouldn’t have seen what a good man he was and Wickham would’ve left Lydia.
On the other hand, if we made Lydia and Wickham the main plot we would lose Jane and Bingley’s plot. We may have references to Jane marrying Bingley, as Lizzie, Lydia and Jane are sisters, but we wouldn’t know about Jane going to London and no seeing Bingley because his sisters and Mr Darcy hid from him that she was there. Although the characters are connected their stories are not because the uniting factor is Lizzie and Darcy’s relationship. It is through Lizzie that the reader discovers Wickham’s past, Jane’s fraught love for Bingley, and Darcy’s connection to all of it. Lydia on the other hand doesn’t know Wickham’s history, she doesn’t speak intimately to her sister Jane, and she persists in the belief that Darcy is an unpleasant man, thus the story would be a very different one.
This isn’t to say our subplots couldn’t interlink, they often do but in the case of Pride and Prejudice these links are familial. Problems arise when we have too many subplots, particularly too many unrelated subplots. As with description and characters too much of anything can be confusing, which is why the Song of Fire and Ice series by George R. R. Martin has an appendix of characters and relationships to help the reader. When we‘re writing first drafts though, this shouldn’t matter, tidying up subplots can wait until editing.