You’ve written your story. However, when you hand out your story to first readers (or beta readers), you receive feedback saying that certain events seemed manipulated by the author.
Maybe your antagonist went easy on your protagonist for some inexplicable reason, resulting in them overcoming the antagonist faster than expected. Maybe your antihero had a spontaneous change of heart the possibility of which had not been foreshadowed at all.
Whatever the case, your characters just didn’t behave like themselves; it felt like someone else was pulling the strings.
You have a broken causal chain.

It is a general rule in fiction that each story event must be caused by the event(s) that precede it. It took me a long time to figure this out personally, but once I did, it came as a revelation. However, when I write a rough draft, I do not always think logically about what event should follow next. I suspect I’m not alone in that either.
We writers need a technique to test the integrity of our causal chains after we’ve finished our first draft. After all, we write what excites us, or what we “feel” should happen next. But when the writing is so raw, the causal link between events is not always there.
Fortunately, there is a way to fix this. In my latest article for The Writing Cooperative, “How to Build Your Causal Chain,” I describe an exercise you can perform to map out your causal chain and spot any breaks in it.
Haven’t started your draft yet? No problem. A slight variation on the same technique can help you in the outlining stage, if you’re the kind of writer who finds outlines useful. I go into it in “How to Build Your Causal Chain.”