Most good stories start with a fundamental list of ingredients: the initial situation, conflict, complication, climax, suspense, denouement, and conclusion. Great writers sometimes shake up the recipe and add some spice.
Initial Situation
Not insane! and the "Evil Eye"
The narrator wants to show that he is not insane, and offers a story as proof. In that story, the initial situation is the narrator's decision to kill the old man so that the man's eye will stop looking at the narrator.
Conflict
Open your eye!
The narrator goes to the old man's room every night for a week, ready to do the dirty deed. But, the sleeping man won't open his eye. Since the eye, not the man, is the problem, the narrator can't kill him if the offending eye isn't open.
Complication
The narrator makes a noise while spying on the old man, and the man wakes up – and opens his eye.
This isn't much of a complication. The man has to wake up in order for the narrator to kill him. If the man still wouldn't wake up after months and months of the narrator trying to kill him, now that would be a conflict.
Climax
Murder…
The narrator kills the old man with his own bed and then cuts up the body and hides it under the bedroom floor.
Suspense
Uh-oh, the police.
The narrator is pretty calm and collected when the police first show up. He gives them the guided tour of the house, and then invites them to hang out with him in the man's bedroom. But, the narrator starts to hear a terrible noise, which gets louder and louder, and…
Denouement
Make it stop, please!
Well, the noise gets even louder, and keeps on getting louder until the narrator can't take it anymore. Thinking it might make the noise stop, the narrator tells the cops to look under the floorboards.
Conclusion
The narrator identifies the source of the sound.
Up to this moment, the narrator doesn't identify the sound. It's described first as "a ringing," and then as "a low, dull, quick sound – much such a sound as a watch makes when enveloped in cotton" (9). Only in the very last line does the narrator conclude that the sound was "the beating of [the man's] hideous heart!" (10)