Straight-line plots work well for short stories, but novels can use several subplots to maintain interest and build suspense. The more developed your characters are, the easier it is to find them. Once your characters come to life, they have a mind of their own and can say and do things that surprise even you. Don’t limit your muse’s ability to inspire you by insisting that your characters behave in a certain way or never do something unexpected. Just think: If it surprises you, won’t it also be interesting to your readers?
As an author, I love it when one of my characters essentially gets out of control. If I don’t know what will happen next, sure that suspense will translate to my readers. It add to the fun of being an author when you don’t know what will happen next, either. There have been times when my characters got themselves into such a mess I had no idea how they’d ever get out. So what did I do? I let them figure it out, and they always did.