In "The Tell-Tale Heart," we see that the narrator has some sort of issue with his mentality. He explains why he thought he had to kill his elderly roommate. The short story explores the human psyche. We are drawn into the mind of a madman. We get a rare glimpse into how someone with a mental problem reacts to certain things. The narrator believes that his roommate, who has an eye condition that makes one eye gray and cloudy, is giving him the evil eye, and that he can see into the narrator's soul. The narrator even tells the reader from the beginning of the story that he has some kind of mental problem.
"TRUE!-NERVOUS-VERY, very dreadfully nervous. I had been and am; but why will you say that I am mad?"
Edgar Allan Poe was a master at suspense. He takes a tale about a man who is mentally unstable and takes us for a ride into madness. The main idea of the short story is how mental illness can make someone so unstable that they are unable to stop the madness in their own minds.
While seemingly a simple story, this Poe classic says a lot about the human mind. For the most part, the narrator reveals the role that guilt can play. He kills the old man because his eye bothers him, but the fictitious sound of a dead man's heartbeat is what dooms him. His guilt is manifest by this heartbeat and leads him to reveal the body and his own crime to the authorities. Basically, a person cannot escape his own guilty conscience; it will make itself evident somehow.