Planning a mystery story seems easy enough for most writers. Decide who the killer, the victim, and the detective are. Give the killer a purpose to commit his crime and the victim a reason to be killed. Piece of cake, right?
Wrong.
A single-plot mystery would be a pretty boring story. Mysteries should be multifaceted, with a main plot and several subplots to keep the reader interested and wanting to know more. Subplots add texture to a mystery story. They can come from many places in your history. These are some of those places where you can find your subplots.
background
Every character in your novel should have some kind of backstory, even if it’s very small. These are great places to find a subplot for your mystery. Maybe your detective was arrested as a kid on suspicion of murder. Or your villain has a secret love for kittens. You can use the backstory to reveal secrets, beliefs, and wishes to make your story more suspenseful or even humorous. The backstory can be used to create or relieve tension.
Secondary characters
These characters are wonderful subplot vehicles. Sometimes a character walks into a story that surprises the writer with how good he is, adding much-needed subplot material. Many times the writer needs to find the character who will do this. Once you decide which characters will be associated with the subplot, make sure you develop that character enough to make it work.
Objects
Mystery stories have many different aspects. One of them is objects. One idea for an object subplot is for the detective to find something that belongs to the killer or the victim, which changes the course of the investigation. There are many different kinds of things that can trigger a subplot.
Theme
The last subplot we will discuss is the one related to the theme. This requires the writer to know what the subject of his story is. Sometimes the topic is known in advance, other times it is discovered during the writing. An example of a thematic subplot is the murder mystery about a murder carried out to prevent the victim from telling the killer’s secrets. The secret can be a subplot that distracts the killer and the detective in their quest to be the victor.
Subplots can work both for and against a mystery writer. Done correctly, they will add depth and texture to a mystery story. If done incorrectly, they will detract from the writer’s plot. Plan your subplots well and you’ll find your readers begging for more.