The Tell-Tale Heart

In the text, the narrator admits to killing the old man was because of his pale blue eye. The narrator becomes so consumed with the old man's eye that he can no longer see the man himself. He then determines to rid himself of the eye by ridding himself of the old man, proving that his crime may not be the act of a sane man (as the narrator claims), but rather, a man suffering from mental instability.

I think it was his eye! yes, it was this! One of his eyes resembled that of a vulture—a pale blue eye, with a film over it. Whenever it fell upon me, my blood ran cold; and so by degrees—very gradually—I made up my mind to take the life of the old man, and thus rid myself of the eye for ever.