Planning a mystery story seems easy enough to most writers. Decide who is the murderer, the victim and the detective. Give the murderer a purpose for committing his crime and the victim a reason to be murdered. Piece of cake, right?
Incorrect.
A mystery with only one plot would be a pretty boring story. Mystery stories should be multi-faceted, with one main and several minor plots to keep the reader interested and wanting to know more. Subplots add texture to a mystery tale. They can come from many locations 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 just a very small one. These are great places to find a subplot for your mystery. Perhaps your detective was arrested as a child 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 increase or relieve tension.
Secondary characters
These characters are wonderful secondary vehicles. Sometimes a character enters a story that surprises the writer with how good they are, adding much-needed secondary material. Often times the writer needs to find the character who will do this. Once you decide which characters will associate with the subplot, make sure you flesh out 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 murderer or victim and to change 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 topic. This requires the writer to know what the subject of his story is. Sometimes the subject is known in advance, other times it is discovered during writing. An example of a thematic subplot is the murder mystery about a murder performed to prevent the victim from telling the murderer’s secrets. The secret can be a subplot that distracts the murderer and 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 subtract from the writer’s plot. Plan your subplots well and you’ll find your readers asking for more.