The narrator has a mental disease and he is the caretaker for the old man that he loves.
Out of the corner of my eye I see the old man that I take care of with a strange eye it looks like the eye from hell, so tonight I shall go to his house while he was sleeping and kill him so he does not spread to his evil eye to the other people
That night I creeped into his room while he was asleep. he did not hear me arrived but soon as I made the slightest sound bounce out of bed looking around and yelled out who's there! I sat in the closet hours none of us made a single noise and it's around an hour later he went back to bed and fell asleep.
So chopped up the old man in the bathtub I did it in the past tub so it will be easier to hide the evidence when the cops are out. And I can just wash it down the drain just before they get there.
As the cops were talking to me I started to get nervous so nervous that my Palms were sweating in my face started to sweat, the cops started asking me questions like how close I was to the old man and how long I knew him.
I started to get so nervous that I started hearing the old man's Hideous Heart Beating voices in my head screaming, I started to feel so guilty that I told the cops rip up the floorboards I killed them and yes it was me I chopped them up in the bathtub go look at the blood under the floorboards was the remaining of his body.