In the beginning of the story the narrator foreshadows how he loved the old man, but it was the eye of the man that motivated the narrator to kill him. This foreshadows that the narrator kills the old man later in the story.
"Nervous--very, very dreadfully nervous I had been and am" (Poe 78)! This quote is an example of an again and again. Poe uses repetition of words to create curiosity, suspense, and suspicion. This also helps develop the mood of the story.
This eye of the old man has been haunting the narrator day and night. The narrator can hear the beating of his heart and can't take it anymore. This drove the narrator to killing the old man by jumping on him with a mattress. This is the Climax of the story.