The narrator is in Jail and he is telling his cellmate the story of how he killed the old man. He tells the story very calmly because he is not insane.
The old man's eye bothered the narrator so much that he thought it was evil. Since he thinks the eye is evil, he is going to kill the old man.
FBI OPEN UP!
He stalked the old man for seven nights at midnight each night waiting to see when he can strike. He says it took hours to even peek his head through the door. After each night when he stalks the old man he watches his eye that he believes is evil
OK I ADMIT I KILLED HIM!
On the eighth night of stalking the old man he ripped him off his bed and took him into the bathroom. As he takes him into the bathroom he puts him in the bathtub and cuts him into pieces so it is easy to clean up the blood.
The narrator takes the plank wood off the ground and puts all the pieces of the old man into the ground but as he is doing that the police show up at his door.
After the narrator is talking to the police acting polite his own heart is beating fast and the guilt gets to him so he confesses.