Despite their diversity, mysteries and thrillers often have a similar basic structure - or, to follow this analogy, similar colors:
The main plot is usually a murder, series of murders, or series of threats of murder or some other form of major destruction. I call this the black thread. But what makes a powerful image is not the black thread in a vacuum, but the way it plays off of the palate of colors around it.
Of equal importance to the murder plot is the green thread. I call this subplot green because it is the quiet, calming storyline that makes us think - or wish - for just a moment that all is going to be OK. This is the subplot that allows the reader a break from action, suspense and tension. The green thread comes in the form of a flirtation or romance, the innocence of a child, a court jester. It is the lighthearted subplot that makes the black thread more meaningful.
But then there's the red thread! This clashing, glaring color ricochets off of the gentle green, because the red thread is the subplot of rain on the parade. This subplot is often the work of a villain unrelated, or seemingly unrelated, to the main plot. The villain may be a character. It may be a natural disaster, or even just a sudden change in the weather. It may be anything that throws a monkey wrench into the story. Multiple red threads of multiple hues are welcomed and encouraged in a good book.
Personally, I like to have a gold thread or two. I see the color gold in association with these subplots, probably because that's the color of the logo for the History Channel. This is a subplot that piques a reader's intellect. It is an element of historical fiction, or the science in a science thriller, or a political maneuver that has never been seen before. It is this thread that lends depth to the story, and readers who like to be mentally challenged eat these subplots up. Those that don't skim over them. And that's OK.
As I complete the tapestry that will be The Vesuvius Isotope, I find myself snipping out a few threads that were misplaced, and then running my eyes over the tapestry as a whole, searching for better places to weave them in. This is one of the fun parts. It's a lot like assembling a jigsaw puzzle. In the second part of this two-part series, I will give a few examples of how I like to see it done.
How do you like to see it done? When you're writing a novel, do the subplots just form, or do you plan them deliberately, choosing your subplots to create your colors?