"I think it was his eye! yes, it was this! He had the eye of a vulture"(Poe 78). The narrator keeps repeating "vulture eye" throughout the story because that leads the narrator to kill the old man.
"And this I did for seven long nights-every night just at midnight-but I found the eye always closed"(Poe 80). This dramatic irony because the old man doesn't know that the narrator is stalking him, but we as the reader do.
"No doubt I now grow very pale;--but I talked more fluently, and with a heightened voice. Yet the sound increased--and what could I do?" (Poe 81). The narrator doesn't know what to do because he thinks that the heartbeat was the dead old man's but it was his own.