Even though he knows that we, the readers, might consider him mad for this decision, yet he plans to prove his sanity by showing how "wisely" and with what extreme precaution, foresight, and dissimulation he executed his deeds. Every night at twelve o'clock, he would slowly open the door, "oh so gently," and would quietly and cunningly poke his head very slowly through the door. It would sometimes take him an hour to go that far — "would a madman have been so wise as this?" he asks, thus showing, he hopes, how thoroughly objective he can be while commenting on the horrible deed he committed.
For seven nights, he opened the door ever so cautiously, then when he was just inside, he opened his lantern just enough so that one small ray of light would cast its tiny ray upon "the vulture eye." The following morning, he would go into the old man's chamber and speak to him with cordiality and friendship.
On the eighth night, he decided it was now the time to commit the deed. When he says "I fairly chuckled at the idea," we know that we are indeed dealing with a highly disturbed personality — despite the fact that he seems to present his story very coherently.
On this particular night, unlike the preceding seven nights, the narrator's hand slipped on the clasp of the lantern, and the old man immediately "sprang up in bed, crying out — 'Who's there?'" He can see nothing because the shutters are all closed. Here, as in most of Poe's stories, the action proper of the story takes place within a closed surrounding — that is, the murder of the old man is within the confines of his small bedroom with the shutters closed and in complete darkness.
