Characters, in a book, come and go. They’re on-scene, then off. Your book will most likely only have 3 or 4 main characters, surrounded by an array of minor or secondary characters. You may have one main plot line, but there can be a second plot line involving the main characters or perhaps with its own characters. Your main character or protagonist probably has a sidekick or confidante. There may be one or two bad guys or one or two romantic interests. There might be a comic relief character or a victim who has to be rescued or avenged.
Although most books focus on a small circle of characters (one main reason for this is so your readers can keep them in their heads and not lose track), there can be a number of peripheral characters.
My question today is: What do those minor characters do when they’re not on-scene? Are they just gone or just doing their own thing sucked up in a plot vacuum? When you’re laying out the plot or timeline of your manuscript, add these characters. For them to be three dimensional, they need to have a life even when not involved in the action. Otherwise, they become stick figures you, the author, push on-stage when you need someone to tell the protagonist a clue or to burst in just in time to distract the bad guy or the police or to appear just in time to take the bullet meant for the lead character.
That doesn’t mean you have to tell or show the readers these characters' lives, but you need to know that they have lives. If you, the author, know the lives and actions of the peripheral characters then it will come through when the character is on-scene. Joe Beetlejuice won’t be in the hardware store for the sole purpose of telling Mr. Do-Gooder about the beautiful young woman being harassed by the bartender at Biker’s Brew Bar. Joe will be there for his own reason. Mr. Do-Gooder will be there for his own reason. And the harassment will come up but it won’t be Joe’s purpose for being there. He has his own life, you know; he does things besides run to places he thinks Mr. Do-Gooder will go so he can supply the inciting information to him to move the plot forward.
So, what do your secondary characters do? Do they have lives they live even when not on-stage? Or do they just lie around while the two or three main characters are performing?
4 months ago