One of the principles I teach my Path of the Storyteller students is the virtue of structuring your story around a single, iconic protagonist on a single, well-defined “mission.”
You can think of the mission as an actively pursued and highly particular purpose. It’s a goal that’s sufficiently well-delineated that, once your readers know about it (which they will, by the end of the first act), there’s an end-of-second-act scene that they can anticipate so clearly, it's like we've made them a promise to get there. And get there we must.
There’s a ton more to say about it, but for the moment, let's use that hero-on-a-mission principle as a simple working definition of plot. What's your hero doing for the whole book? That's the plot.
But you know and I know that novels are not bare-bones affairs. Even highly focused, novella-length works (I’m thinking about A Christmas Carol ...