This is one of Poe's most famous stories and was first published in 1843. It is a horror story told in the first person where a murdered tries to convince the reader of his sanity.
Narrator: He claims he is sane but suffers from nervousness. Um, yeah.
The Old Man: The guy the narrator lives with and murders.
This crazy dude lives in a house with this old man. He doesn’t like the old man especially his weird eye. So he decides to kill the old man.
So one day he goes into his room and kills the guy. Then he cuts the guy up and buries him under the floorboards. Then the police come.
They search the house and don’t find anything, so they are convinced. The only problem is that this crazy dude keeps hearing the old man’s heartbeat. Get it? The 'Tell Tale Heart'?
This drives him nuts and then he confesses to the cops.