The narrator tells us he is not mad, just nervous-- very very dreadfully nervous. The narrator wanted to kill the old man because of his "vulture eye". The narrator is the antagonist in the story and the setting is in he old mans chamber.
In the story the narrator wants to prove his sanity, yet he wants to kill the old man. He is kind to the old man for a whole week before he kills him. A 12:00 am he would look in at the old man. He opens the lantern to see if the old man's "vulture eye" is open. He then asks the old man how he had slept.