"The Tell-Tale Heart"(1843) explores a murderer's guilt for killing an old man who had a vulture-like eye. The tale begins with the narrator/murderer musing how his madness strengthens his senses and how he's uncertain of where the thought of murder originated. However, the old man's eye became the center of the situation. The old man's eye was pale bule and had film over it, resembling that of a vulture (Poe, 1843), causing an uneasiness in the narrator. 

"...it was impossible to do the work; for it was not the old man who vexed me, but his Evil Eye."

This uneasiness and the negative effect the old man's eye has on the narrator makes him eager to get rid of the eye which leads to killing the old man. Every night while the old man was asleep, the narrator would attempt to kill the old man but would stop short because he couldn't see the "evil eye".  If there was no eye, it would just be killing an innocent old man, the narrator concludes. This went on for seven nights, until on the final night, the narrator accidentally wakes the old man up. As he waits in silence for old man to fall asleep, he opens the lantern in his hand ever so slightly and the light falls directly onto the old man's "evil eye". 

...at length a single dim ray, like the thread of the spider, shot from out the crevice and fell full upon the vulture eye. ...now, I say, there came to my ears a low, dull, quick sound, such as a watch makes when enveloped in cotton. I knew that sound well, too. It was the beating of the old man's heart. It increased my fury, as the beating of a drum stimulates the soldier into courage.

Most importantly, with the light on the old man's eye, his heartbeat becomes discernible. The heartbeat now has the narrator's attention and pushes him off an already thin edge. As a result, the narrator leaps into the room, drags the old man off the bed and palces the bed over him, effectively stopping the heartbeat. The narrator promptly disposes of the body under the floorboards and not long after, the police show up at the house. While the narrator causually talks to them, he begins to hear the thumping of the old man's heart beneath the floorboards. The sound intensifies and the narrator seems to be the only that can hear it. Not able to take it any longer, the narrator to confesses to his crime in the heat of the moment and tells the police where the old man's body is located.  

Anything was more tolerable than this derision! I could bear those hypocritical smiles no longer! I felt that I must scream or die! --and now --again! --hark! louder! louder! louder! louder! --
"Villains!" I shrieked, "dissemble no more! I admit the deed! --tear up the planks! --here, here! --it is the beating of his hideous heart!"

The monster in the short story is the narrator and the site of monstrosity is the narrator's irrational fear. The narrator is consumed by this fear of the old man's eye, which is then heightened by the heartbeat that only he can clearly hear. Although the fear/madness supposedly heightens the narrator's senses, he is utlimately consumed by it and is pushed to kill, as the narrator stated, an innocent, kind man. The murder of an innocent elderly man reveals the dark side of human nature (Womack, 2001), a sight of monstrosity that turns a seemingly stable person into a monster. However, unlike the narrators from "The Black Cat" or "The Cask of Amontillado", this narrator confesses to their sins, albiet through the coaxing of a heartbeat, leading to the possibility of redemption for a monster. Furthermore, the old man's eye could also be labelled as a site of monstrosity because of the narrator's strong reaction to it. His eye fuels the narrator's paranoia which leads them to devise a plan to remove it because of the death it represents. The narrator described it as vulture-like and vultures are scavengers; they signal the presence of death, according to this belief, the narrator tries to escape death.