The author was vexed by his father's disgusting eye, and decided to end his life to get rid of it. The author planned to be surreptitious and have his intentions undiscovered.
For the next several nights, at midnight sharp, the author warily enters the old man's chamber, and ever so cautiously points a lantern at his eye. The eye was closed, and the author could not bring himself to kill the old man, for it is the eye that makes him uneasy, not the old man himself
HA HA HA! Time to meet your demise old man..
One night, the author accidentally made a slight noise, and the old man, being afraid of robbers, sat up, wide awake. The author knew the old man could not see him, so he waited about an hour before throwing the man onto the floor and strangling him to death. He then secured the corpse under the floor of the old man's chamber.
A couple of police officers arrived with a complaint from the neighbors about domestic disturbance. The author, having nothing to fear, munificently let them inside and allowed them to search the house.
The cops and the man sat down in the old man's chamber and spoke pleasantly. However, the man kept hearing a muffled thumping noise from underneath the floorboards. He believed the cops had heard the "old man's heart" as well and suspect that the man was guilty.
I can't take this derision! They know! They suspected me all along
The man could not take the mockery anymore. He could not stand the beating of the "old man's heart" (actually the sound of his guilt) anymore. He threw open the floorboards and screamed out loud that he had MURDERED the old man.