Edgar Allan Poe 
The tell-tale heart 

True! nervous, very, very dreadfully nervous I had been and am; but why will you say that I am mad? The disease had sharpened my senses, not destroyed, not dulled them. Above all was the sense of hearing acute. I heard all things in the heaven and in the earth. I heard many things in hell. How then am I mad? Hearken! and observe how healthily, how calmly I can tell you the whole story.