In Edgar Allan Poe's "The Tell-tale Heart," the author uses several techniques to convey discovery.
Unlike Poe's previous story of horror and murder "The Black Cat," here the author uses dramatic dialogue—where rather than having discussions with other people, he speaks directly to the reader. While the speaker is trying to convince his audience that he is sane, the very condition of insanity in his ramblings allows the reader assume with some certainty that the unnamed protagonist will be discovered, for he has no logical defense.
Of his delusions, the narrator's mental condition is clear when he claims:
I heard all things in the heaven and in the earth. I heard many things in hell.
With an inability to connect with the real world, the reader can anticipate that the narrator will never hold up under close scrutiny from the outside world.
His obsession is clear through his use of personification.
It is impossible to say how first the idea entered my brain; but once conceived, it haunted me day and night.
The device of personification gives life to inanimate objects as if they were alive. His idea does not live or breathe; it cannot enter or depart; and, it cannot haunt.
The reason for the narrator's obsession to kill the old man is his "evil eye." While the speaker tries to tell the audience that this is the cause of his desire to end the old man's life, we can arguably infer that symbolism is used here, and perhaps it is this literary device that most lends itself to the theme of discovery.
[A symbol] is something [that] is itself yet stands for or means something else….
A symbol is a sign [that] has further layers of meaning.
The eye is not evil: this is part of the speaker's delusional state. However, an eye is symbolic of knowledge and truth.
Other qualities that eyes are commonly associated with are: intelligence, light, vigilance, moral conscience, and truth.
The old man's eye is only "evil" based on the narrator's skewed perception of reality. In essence, though it is cloudy, the eye may be symbolic of seeing beyond the narrator's subterfuge, to the truth of what he plans to do. The cloudiness may symbolize the old man's infirmity and inability to know what the narrator is planning.
It seems as if he will succeed with his heinous act:
I smiled, --for what had I to fear? I bade the gentlemen welcome.
However, the eye symbolizes the ability of the truth to make itself known. This suggests that the actions of the speaker will come to light, and his deed be discovered. The shriek of the old man was heard in the night, and the police come to investigate. The truth is revealed at the end when the narrator manically admits to the police what he has done to the old man.
"Villains!" I shrieked, "dissemble no more! I admit the deed! --tear up the planks! here, here! --It is the beating of his hideous heart!"
For more analysis of Poe's "The Tell-Tale Heart," check out this video: