There are a lot of people who view all sub-plots with the gravest suspicion, regarding them at best as a pointless distraction from the main business at hand, and, at worst, as a dangerously amateurish self-indulgence. Kill your darlings, they screech like dogma-drilled harpies, kill, kill, kill them all! Needless to say, I disagree.
In a general sense, I’m all in favour of sub-plots. In fact, I delight in them. They offer so many exciting possibilities to writers of fiction, open up so many interesting roads of expression, and gift us so many new dramatic opportunities - and, as an added bonus, a lot of these opportunities crop up entirely unexpectedly. That’s a big part of their charm.
As your novel progresses and your fictional world grows larger and ever more complex, these highways and byways jump out at you like road-signs on a foggy day. Some days you immediately know that taking a little detour would not only be interesting, but might even be necessary for your story’s health and vitality. Sometimes you want to know where the road goes just for the sake of it, maybe simply because it’s got an interesting name, and that’s a good enough reason to go exploring. If things happen to go wrong, there’s nothing to worry about. You have a full tank of gas. Turn back, try a different route.
Done just right, sub-plots illuminate and beautify your novel’s darker, more desolate regions, rescuing them from the threat of torpor and the dangers of ennui, and bring a whole new range of colour to a fictional landscape that you might have believed you already knew like the back of your hand. Being proved wrong like this can be a real, genuine pleasure. In a way, writing fiction is just like any other craft or skill, or, in fact, like any other aspect of life – the more you learn, the more you understand how much more there is to learn; the more you know, the more you understand how little you really know.
Uncertainty of this kind is good, because it’s the opposite of complacency and blind, inflexible dogma. Confronting the new and the unknown head-on and exploring the possibilities, however diverse or disturbing, is good, because it’s the very opposite of stagnation and denial. That’s why life is an adventure, and not a predictable theme park ride, endlessly circling the rails and eliciting the same old screams in the same old pattern. Life keeps you on your toes, and so should both writing and reading fiction, because the best fiction doesn’t only entertain and distract, it reflects our lives, sometimes from angles we may never have considered before.
The very best sub-plots mostly run more or less parallel to the main plot, and either mirror, contrast, or even subvert your novel’s primary theme, allowing your reader to enjoy the story from a variety of different viewpoints, and inviting them to immerse themselves ever deeper in their willed suspension of disbelief. Once you have them in that almost hypnotic state of suggestion, you can really begin to put them through the wringer. You can make them laugh, you can make them cry; you can make them shudder, cringe, and moan.
Seduced by a story broadened and enriched by subplots, all aping the texture of the real world, they’re putty in your hands. And they love it. You love it, too, because if you’re a writer, you’re also a reader.