The reader also discovers (with the introduction of Pluto into the story) that the narrator is superstitious, as he recounts that his wife made "...frequent allusion to the ancient popular notion, [that] all black cats [are] witches in disguise." Even though the narrator denies this (much as the narrator in denies that he or she is insane), the reader becomes increasingly aware of his superstitious belief as the story progresses.
At that point, the rest of the story is told in flashback, as the narrator pens "...the most wild, yet homely narrative...[whose] events have terrified--have tortured--have destroyed [him]."
My Worst Nightmare (A Short Story) - Marked by …
However, are the events of the story, as the narrator suggests, based upon "...an ordinary succession of very natural causes and effect," or are they indeed caused by the supernatural?