The narrator lives in the late 1800's, with an old man sporting a glass eye. This false eye irritates the narrator and drives him to insanity. He makes a plan to kill the old man and finally rid himself of the vulture eye. The narrator enacts this careful plan, taking extra care in its practice. He swears upon his life he is not mad.
The Next Day...
The narrator slips his way into the old man's room for seven nights, observing his sleeping body and waiting for the right moment, when the eye was open. And every day when the old man awakes, he acts like nothing unusual has passed. He treats him especially well, to ensure the old man doesn't suspect a thing. And with this routine, he awaits the day where the old mans evil eye is open. Then, and only then, will the narrator strike.
The day finally comes! It is the eighth night, and the old man's eye is open. The narrator is filled with rage at the evil eye and hears the beating of the old man's heart. He is overwhelmed with madness and strikes. He smothers the old man, dismembers his corpse, and stuffs him under the floorboards.
The next morning, the police arrived. They came to investigate a scream in the middle of the night. The narrator, confident in his own ability, denied all claims and even invited them to stay and chat. The narrator saw the light at the end of the tunnel. But then, something started happening. A dull thumping sound...like something the narrator had heard before...
The thumping of the old man's heart! The narrator's thoughts became erratic and he felt himself sinking deeper into madness. The noises grew unbearably loud, and with a cry the narrator threw himself to the ground and confessed. He admitted to killing the old man, declaring that his corpse was underneath the floor boards. He was rightfully arrested.