The opening paragraph foreshadows the murder by letting you know that the narrator is mad.
Foreshadowing is when the author gives hints early in a story to something that will happen later. Foreshadowing adds to the suspense of a story and makes the reader interested. Foreshadowing is especially important in the beginning of a story.
In the opening paragraph, we learn that the narrator is nervous, and that he is insane. Both of these things foreshadow his murder of the old man.
The disease had sharpened my senses—not destroyed—not dulled them. Above all was the sense of hearing acute. I heard all things in the heaven and in the earth. I heard many things in hell. How, then, am I mad?
When he says that he is not mad, that is further proof that he is. He is denying it because he is nervous that you will recognize it. He also talks about how he is nervous but fine. This is also proof that he is insane. When the narrator talks about hearing things “in Hell” then you really know that he is nuts. He also asks you to listen to him. Many madmen want to prove to you that they are not mad.
Let’s look again at the very first sentence.
TRUE!—NERVOUS—VERY, very dreadfully nervous I had been and am; but why will you say that I am mad?
The narrator asking if you will say that he is mad, tells you that other people have told him he is mad. This is definitely a warning sign, it is also foreshadowing. It means that he has done crazy things in the past.
In fact, throughout the entire story he will try to convince us that he is not crazy while carefully describing the crazy things he does. He kills the old man for his evil eye, chops up his body and hides it under the floorboards, and then leads the police right to the body and confesses because he thinks he can hear the beating heart! The man is crazy. It was all foreshadowed in this paragraph.