Appropriately enough, the pacing of "The Tell-Tale Heart," the story's tempo, resembles that of a human heart.

At first, when the unreliable narrator appears relatively calm, the pace of his words is quite leisurely. This is a deliberate strategy on Poe's part to make his narrator at least somewhat believable, even if we don't find him completely reliable.

If the narrator had started off in a crazed mood, with his words delivered in the tempo of a fast-beating heart, then we would have dismissed him right off the bat as a madman, and therefore, his story would not have been as interesting.

But the slow change in tempo allows us to be drawn into the narrator's story until, as the pace of his words becomes faster and faster, we are confronted with an insane killer. Yet before then, Poe deliberately slows down the pace to good effect, heightening tension as the narrator slowly but surely sneaks upon his victim, the old man he's going to murder.

Poe's remarkable ability to adjust the pace of the story not only makes the narrator a more believable character; it also makes "The Tell-Tale Heart" more effective as a horror story.