it was his eye! yes, it was this! One of his eyes resembled that of a vulture—a pale blue eye, with a film over it. Whenever it fell upon me, my blood ran cold.

The narrator's inability to coexist with this eye foreshadows his murder of the man. As he plots his crime, he finds that he is unable to carry it out as long as the eye remains closed. He stalks the old man for seven nights unsuccessfully. On the eighth night, the eye is open; the source of his vexation can now be eliminated.

In this same paragraph, he foreshadows his eventual actions in his comment that "it is impossible to say how first the idea entered my brain." Although it isn't clear what "idea" the narrator has conjured against the man, he also relates that it "haunts" him, providing a negative connotation for the context of those plans.

Poe establishes an eerie mood through heavy foreshadowing, particularly early on in this tale.

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.

The foreshadowing in Edgar Allan Poe's The Tell-Tale Heart begins with the title, although the narrator makes no reference to the old man's titular heart until well past halfway through the story. It's then, however, when it's first mentioned, that the heart becomes the absolute central element of the story.

After that, the evil, pale blue, filmy, vulture eye that so incenses the narrator and drives him to murder the old man is mentioned only once again, after the old man is dead.

He was stone dead. His eye would trouble me no more.

The narrator's focus then shifts to the old man's heart.

After the title, the foreshadowing continues in the very first sentences of the story.

TRUE!—NERVOUS—VERY, very dreadfully nervous I had been and am; but why will you say that I am mad?

The narrator knows the end of the story, but the reader doesn't. At this point, the reader doesn't know why the narrator is so "dreadfully nervous," and the reader has no reason, as yet, to think that the narrator is mad.

It's not until the narrator tells the story, or most of it, that the reader understands what the narrator means by that first sentence.

The disease had sharpened my senses—not destroyed—not dulled them. Above all was the sense of hearing acute.

As with the narrator's references to the "tell-tale heart" and madness, the meaning of the narrator's reference to his acute sense of hearing is also beyond the reader's understanding until much farther into the story.

In the first part of the story, the narrator focuses on his sense of sight and the old man's evil vulture eye. The narrator mentions his and the old man's hearing only in passing, until the narrator notices the sound of the old man's beating heart. This is when the beating heart becomes the narrator's obsession, and drives the rest of the story forward.

It increased my fury, as the beating of a drum stimulates the soldier into courage.

There's one more example of foreshadowing in the opening paragraph of the story.

I heard all things in the heaven and in the earth. I heard many things in hell.

Driven by his rage at the sight of the old man's vulture eye and by the sound of the "hellish tattoo" of the old man's beating heart, the narrator kills the old man, dismembers the body, and places the dismembered parts of the body under the floorboards of the house.

I then replaced the boards so cleverly, so cunningly, that no human eye—not even his—could have detected any thing wrong.

"No human eye" could have detected the old man's body under the floorboards. However, the narrator's superhuman sense of hearing could hear the old man's beating heart, which drove him into the hell of madness, and then into the madness of hell.

Right from the beginning, we realize that the narrator well-spoken but is also trying to convince the reader (and himself!) that he is sane even though he apparently is being accused of being otherwise.  By mentioning the imagined sounds from hell, we realize that the narrator is indeed "unwell" and only evil things will be revealed in the story, otherwise the narrator's obsession with being deemed as sane would most likely not be there. In addition, to want to harm a person merely based on his eye, which is perceived as hideous (he claims he loved the man, doesn't desire his gold, and has never been wronged by him) is completely illogical and confirms our suspicion of his mental instability.

The Tell-Tale Heart begins with language that not only draws the reader into the story, but also lets you know that this narrator - clearly, a mentally unbalanced person - is telling you about something that has already happened. So, in a sense, he is not foreshadowing, but rather flashing back to an event in his past. But language like, "I heard all things in the heaven and in the earth. I heard many things in hell," definitely lets the reader know that this is not going to be some nice, happy story - Poe sets the stage for a sinister tale of madness. Check out the link below as well as other good articles at eNotes on Poe!

An interesting parallel can be observed between this short story and Poe's "The Black Cat." In both the narrator goes to great pains to prove to the reader that he is not crazy but rather confirms by his manner and speech that he really is.

"The Cask of the Amontillado" is another confessional narrative, but unlike the first two stories, the narrator here had a definite motive (revenge) and is not necessarily insane.

By beginning this story with an exclamation, Poe already has his audience's attention. What' more, he asks the reader to determine his level of sanity with the rest of the introduction. By starting out this way, the reader is now intrigued, and wishes to move forward to answer the question posed.

This introduction works a lot like ledes in journalism -- they are meant to grab the reader's attention with a "hook" of some sort that the reader then has to know more about. Poe has accomplished this well by opening the story in the way that he does.

"TRUE! nervous, very, very dreadfully nervous I had been and am; but why WILL you say that I am mad?"

By starting the story with the narrator asking the audience to judge his sanity, Poe is creating an atmosphere of mystery and suspense. Immediately the reader begins looking for signs of true insanity. The result is a short story that is more psychologically oriented than externally oriented. As the narrator continues to defend his sanity by showing the rational thoughts and actions he had in dealing with the gray eye, the reader is made more and more aware of the mental disease plaguing the narrator. While there is much external conflict, the focus remains on the mental state of the narrator, and to the driving force behind the action. Through this focus, Poe is able to create a story that is horrific both in the physical action and in the mental implications, appealing to multiple audiences.

The syntax that Poe uses in the narration of "The Tell-Tale Heart" is not the calm, cadenced sentences of someone who might be writing in a journal or a newspaper. Instead, it reflects the ramblings of an unstable person who is trying to convince others, and maybe even himself, that he is not a madman. At the end of the story, he imagines that he hears the old man's heart beating beneath the floorboards where he has hidden the body. This may have happened because of an overwhelming sense of guilt, or of ongoing terror of the old man, or perhaps both. The point is that the story is narrated in the aftermath of the event, and the deranged narrator is attempting to work out and explain what happened.

If we examine the story's syntax, we can see that Poe is mimicking the thought patterns of an unstable man. He begins with an exclamation: "It's true! I have been ill, very ill." Right away we question the man's veracity. The narrator puts frequent questions to readers and then answers them himself. "Is it not clear that I am not mad? Indeed, the illness only made my mind, my feelings, my senses stronger, more powerful." The narrator uses this question-and-answer syntax to try to convince readers (or listeners) of his sanity, but readers will undoubtedly come to the opposite conclusion.

The frantic confessional tone is reflected in the beginning of the second paragraph as well: "Listen! Listen, and I will tell you how it happened." Again at the beginning of the fourth paragraph the narrator writes, "So you think that I am mad? A madman cannot plan." If you go through the rest of the text, you will find many more examples of exclamations followed by explanations, and questions followed by answers. Poe uses this mood-inducing syntax throughout the narrative to draw readers into the mind of this madman who has cold-bloodedly committed a horrific crime. Its effect is frightening as we realize the lack of real logic in the thoughts of a murderer.

In the first paragraph, he refers to madness.  Right off the bat he defends himself against an unheard accusation of madness.  We haven't accused him of being mad, but after we read his reason in paragraph 2, we just might.  So, he jumps the gun stating, "why will you say that I am mad?...How, then, am I mad?"  Already, we are intrigued, and wondering why he is ranting about being mad.  He has obviously done something for which he feared we would accuse him of madness, and felt the need to defend himself by telling his tale.  He claims that he isn't mad at all, because if he were, he wouldn't be able to "healthily...calmly...tell you the whole story."

Now we are prepared to hear the 2nd paragraph.  In it he talks about the fact that he made up his "mind to take the life of the old man."  Before this, he said there was no provocation excepting the old man's " eye of a vulture—a pale blue eye, with a film over it".  We certainly would think he is mad if that is the only motive for murder that he gave.  So, the first paragraph preempts our assumption of him being mad.  He predicts we would think that, and to reject that idea, he mentions it.