The narrator wants to kill the old man because of his eye.
The old man's eye is driving me crazy, I must end the old man's life.
Exposition
The narrator stalks the old man for several nights because he won't kill the old man until he sees his eye.
I need to see the old man's eye before I rid him of his life!
Rising Action
The narrator shines a light at the old man's eye...
Who's there?!
Climax
Falling Action
The narrator kills the old man and hides the body.
I will hide the evidence and I am beyond confident that no one will ever find out. I am so clever and I am cunning, however I am NOT crazy nor mad.
Resolution
The narrator is so confident of his work that he brings the officers to the same room that the old man's body is hidden. However the guilt has caught up to the narrator that he can hear the heartbeat of the old man.
Thump, thump...Thump, ThumpTHUMP, THUMP
Over here officers.
Resolution
I admit it, killed the old man!
The narrator confesses because he couldn't handle the guilt.