The narrator is uneasy about the old man. he had never troubled him, there was just something wrong.
The narrator is convinced it is the old mans eye that is vexing him. He also tells us that the disease has only sharpened his senses.
The narrator visits the old man in his room every night at midnight the week before the murder.
The narrator is caught while watching the old man on the night of the murder and dismembers him in the bathtub so there would be no blood stains.
Police officers show up to the old mans house because one of the neighbors called in the night because the scream the heard aroused suspicion of foul play.
The narrtor welcomed the police and offered them a seat in the old mans room. The narrator seemed perfectly sane and would have gotten away with it , but his overwhelming guilt made him confess to the murder and he was taken in.