What we know is that this guy is distraught, lying to us, damned, and apparently about to die. His introduction to this tale and his requests of us as his readers constitute the story’s initial situation.
William Wilson’s double is definitely the story’s central conflict, bringing with it important questions: who is this guy? What is his relation to our narrator? What does he want? Why does he torment William so much?
Of course, the various hints we’ve gotten so far have clued us into the fact that this second William Wilson is no mere ordinary, coincidentally named guy. We know he has some special connection to the narrator, and probably suspect that he isn’t actually a real person. But the narrator isn’t so perturbed until this pivotal scene.
This would seem to be the sudden and brutal fall into utter evil that Wilson spoke of in his introduction. We’ve been building toward this moment, when Wilson finally confronts the other Wilson, since the story’s start.
Wilson is on the verge of discovering the truth…
The denouement is the stage when everything finally gets explained. This story doesn’t work exactly like that, in the sense that we’re not sure how enlightened the narrator is, even after his confrontation with his double. Does he believe that this other William Wilson was a physical manifestation of his conscience? Or is he still confused? Can we even be sure as to how to interpret the bloody finale? This denouement leaves more questions than it answers.
As in the denouement, there’s no clear explanation in this conclusion. See “What’s Up With the Ending” for a few possible interpretations.