For much of my early writing life, I considered the B-story a companion to the A-story. A break from the action, perhaps a palate cleanser or a chance for the protagonist (and the reader) to rest before the next big conflict. And it can definitely be those things. But in a three-act story structure, the B-story is also much more than that. It represents your protagonist’s internal story arc and helps them to transform into who they need to be to achieve the story’s main goal.
