Poe was always concerned about the emotional effect of his story upon the reader. In "The Tell-Tale Heart" we can find ourselves identifying with the old man lying in bed fearing for his life. We do not identify with the narrator because he is obviously insane. But we know how the old man is feeling because we have all had the same feelings the narrator attributes to the old man, if only in childhood.
I knew that he had been lying awake ever since the first slight noise, when he had turned in the bed. His fears had been ever since growing upon him. He had been trying to fancy them causeless, but could not. He had been saying to himself—“It is nothing but the wind in the chimney—it is only a mouse crossing the floor,” or “It is merely a cricket which has made a single chirp.”
Houses can make strange sounds at night. They are almost like living creatures. They settle just a fraction of an inch, and the timbers make a creaking noise. The wood tends to expand or contract with the temperature and the weather. It can pull on the iron nails just a tiny bit and make eerie sounds, sometimes like the hinges of an opening door. We lie there wondering what that was and whether we will hear it again. We would like to go to sleep, but we are afraid to lose consciousness. Going to sleep means trusting the whole world to leave us alone. It is easy to imagine that a squeaking timber is a footstep on the stairs. And then it is easy to go further and imagine an intruder creeping up on us with evil intentions. Samuel Taylor captures this feeling perfectly in one of the stanzas of "The Ancient Mariner":
Like one that on a lonesome road
Doth walk in fear and dread,
And having once turned round walks on,
And turns no more his head;
Because he knows, a frightful fiend
Doth close behind him tread.
In the old man's case, the frightful fiend is all too real. The madman who is telling this story corresponds to our own worst fears. He does just the sorts of things we can imagine when we are lying awake in the dark listening. If there is no sound we imagine the maniac is watching and waiting. He wants us to be satisfied that there is no danger. He is waiting for us to turn over in bed and close our eyes. Then, like the narrator of "The Tell-Tale Heart" he will spring.
The old man's hour had come! With a loud yell, I threw open the lantern and leaped into the room. He shrieked once—once only.
Even while lying awake in terror we often finally fall asleep and wake up the next morning with the sun shining and realize that it was nothing but our imagination.