The narrator foreshadows his insanity in the beginning. In the first paragraph it says , "It is impossible to say.....and thus rid myself of the eye forever" (Poe 78) . This quote shows that Poe is positive that some time in the story he will kill the old man.
There are many similes found in "The Tell-Tale Heart" the one I chose is, "So I opened it - you cannot imagine how stealthily, stealthily - until at length a single dim ray like the thread of the spider shot out from the crevice and fell upon the vulture eye." The simile that is used here is how the a dim ray is compared to the thread of a spider.
The theme of this story is to not commit crimes or wrong doings because our own guilt can expose us because the truth has a louder voice than lies. The short story is teaching the reader that lies and crimes cant be hidden forever.