Subplots perform several functions – they add depth and resonance to your story by inviting comparison to the main plot, allow for variation to the tone and pace, often through comic relief, and cause deviations to the plot itself. Linda Seger remarks that subplots give your protagonist an opportunity to smell the flowers, to fall in love, to enjoy a hobby, or to learn a new skill. Subplots also echo the main concerns of the story at a more transcendent level, by adding a different perspective, enriching the tone, and strengthening the themes and symbols of your story. But subplots are not only concerned with protagonists and their world. An action originating from a minor character within the subplot, may twist the plot around in a surprising way. Indeed, crafting a turning point from the subplot is one way to ensure that you don’t telegraph the event and ruin the surprise. Like the main plot, a subplot has a beginning, middle, and end. The number of subplots depends on the needs of the main plot, and how much underpinning it requires.
Sherlock Holmes – Main Plot
In the 2009 movie Sherlock Holmes, Holmes (Robert Downey Jr.) tries to stop Lord Blackwood (Mark Strong) poisoning all opposing voices in parliament, installing himself as leader of the nation, and extending the Empire. A declared practitioner of the dark arts, Blackwood personifies the forces of irrationality, Holmes, the forces of logic. At a thematic, moral, and symbolic level, the premise is of cool-headedness and rationality vs. fear and irrationality.
Enriching the story are three subplots: that of the mysterious Professor Moriarty who, behind the scenes, manipulates the conflict between Lord Blackwood and Holmes, and in particular, Irene Adler’s (Rachel McAdams) love for Holmes, for his own evil ends; the Holmes/Dr.Watson/Mary Morstan triangle; and Holmes’s own relationship with Irene Adler. Some of the major deflections to the main plot come from these subplots: Moriarty gets Irene to drug Holmes in his own rooms by threatening to kill him if she doesn’t (subplot 1). Irene has access to Holmes because of her (past) relationship with him (subplot 2); meanwhile, Holmes tries to break up Watson’s (Jude Law) relationship with his girlfriend, Mary Morstan (Kelly Reilly), perhaps for fear of losing his only friend and confidant (subplot 3). Holmes’ antics succeed in making Watson feel guilty about abandoning his old friend, which results in his saving Holmes’ life on several occasions (main plot). Coincidently, the Watson/Mary relationship invites comparison to the Holmes/Irene one, suggesting an even tighter bond between the two men. In this way, events and motivation from a subplot serve the main plot, helping to keep it on track.
The function of subplots, as shown in Sherlock Holmes, is to explain and motivate character actions, deflect the main plot, and deepen resonance through contrast and parallel. Although subplots vary substantially in focus and emphasis from story to story, the use of the three aspects identified above will certainly help to deepen and enrich any plot.