Lately I've been listening to the Mythcreants podcast, and a recent topic was throughlines: 131 - Throughlines - Mythcreants I'd never thought of the things they address in the context of that term, although other terms and phrases relate, like "what's it about," "what's the heart of the story," "theme," and so forth. It's an interesting discussion. Problem areas like beginning too early, knowing where to end the story, switching the "throughline" midstream, what constitutes a prologue and whether there should be a prologue-ish opening, are addressed. Having a clear idea of the throughline can help you stay on course in the story. For a conceptual visualization of the throughline, I've been thinking of a type of may pole dance in which the ribbons are plaited down the pole. The pole is the throughline, and everything more or less circles it; the pole is the guide, the crux, the central structure holding everything else together. Edit: Also, I think, the throughline should be something the reader will recognize and experience, even if it's not always explicit. It's a little more solid than something like theme. In a way, it relates to the promises we make, the hook, etc.